Often people underestimate the shear efficiency of the death camps. People would be unloaded from the suffocatingly cramped cattle cars in small, easily manageable groups. On the unloading dock the young and able bodied would be separated from the women, children, and elderly to be sent to the work camps. Thus in one fell swoop anyone with the physical ability to resist was removed. There are reports of people attempting to fight the guards, but the SS were armed and obviously didn't particularly care if they had to kill you now or a few minutes later. Families were often grouped together as it kept many docile for fear of their loved ones being punished. From there on, the time til being forced into the gas chambers would be about 10 minutes, no time at all to organize any sort of real resistance. Rumors were abound in the period, some true, but many not. Certainly some realized before the end what was coming, but by the time one reached the camps it was far, far too late.

However, there was at least three instances of major resistance in the camps. To save on costs, the Nazis took to using Jews to perform minor tasks. Maintenance, cleaning, moving corpses from the gas chambers to the crematoriums, etc. Known as Sonderkommandos, these men and women were kept heavily guarded and replaced about every 4 months. Despite this, the Sonderkommandos were the primary resistance groups in the camps. They were the originators of the rumors you describe, a desperate attempt at warning those still outside. In 1943 Sonderkommandos held revolts the Treblinka and Sobibor death camps, allowing about 400 people to escape. Although most were later recaptured and killed, they represent the most successful attempts at resistance in the death camps. The action was so embarrassing to the Nazis that Treblinka and Sobibor were closed and their existance covered up. A similar plan at Auschwitz in 1944 was foiled when the Nazis decided to move up the replacement date of the Sonderkommandos there. They manged to damage a crematorium and kill 3 SS guards before they were rounded up and executed. Of the several thousand Sonderkommandos, less than 20 survived the war.

More on the Sonderkommandos: http://en.wikipedia.org/wiki/Sonderkommando

Yep. There was often spontaneous resistance and hysteria from people who realized that something was very wrong, as they were herded into the chambers. According to Rudolf Hoess (commandant of Auschwitz camp):

"Still another improvement we made over Treblinka was that at Treblinka the victims almost always knew that they were to be exterminated and at Auschwitz we endeavored to fool the victims into thinking that they were to go through a delousing process. Of course, frequently they realized our true intentions and we sometimes had riots and difficulties due to that fact."

Source: http://www.fordham.edu/halsall/mod/1946hoess.html

Touching on the hysteria part of your question, Laurence Rees' book 'Auschwitz' describes mismanagement of the Treblinka death camp in 1942 because apparently the gas chambers were not big enough for the task as more and more victims arrived, this led to the breaking down of the subterfuge that the camp's showers were for disinfecting the prisoners, so SS troops were firing down at the crowds from rooftops. 'The air was filled with screaming and weeping' an eyewitness in the book states. (Pg. 200-201)

There were rumors about horrible things happening, but there was hope. But the 'hope' was a mind-fuck designed into the system that helped reduce resistance.

Maybe they had a letter that said they were an essential war worker. Maybe they had served valiantly in WW1. Maybe they had an important role on the council that administered the ghetto.
Maybe they had blue card that was handed out, and only the people with red cads were being sent 'to the east'.
Maybe the train they were on was going to a work farm. Maybe they were at a transit station.

By the time they were naked and being chased down a barbed wire corridor into a gas chamber, whipped and hit by rifle butts the whole way, it was much too late.

EDIT - These psychological techniques (false hope, false choices) are one of the main subjects of 'Treblinka' by Jean-François Steiner

In response to your first question, newcomers to the camps were subjected to an entry ritual that was designed to shock them and take away their ability to resist.

Other prisoners that were already in the camp looked on newcomers with disdain, which made coordination among the prisoners difficult. In any case, there were not enough rations in the camp for all the prisoners, which made prisoners see each other as competition.

Primo Levi wrote about his experience in Auschwitz, the following extract is from his book The Drowned and the Saved:

…kicks and punches right away, often to the face; an orgy of orders screamed with true or often simulated rage; complete nakedness after being stripped; the shaving off of all one’s hair; the outfitting in rags. It is difficult to say whether all these details were devised by some expert or methodically perfected on the basis of experience, but they certainly were willed and not casual: it was all staged as was quite obvious.

Nevertheless the entry ritual, and the moral collapse it promoted, was abetted more or less consciously by the other components of the concentration camp world: the simple prisoners and the privileged ones. Rarely was a newcomer received, I wont say as a friend but at least as a companion-in-misfortune; in the majority of cases, those with seniority (and seniority was acquired in three or four months; the changeover was swift!) showed irritation or even hostility. The “newcomer” was envied because he still seemed to have on him the smell of home, and it was an absurd envy…

[The newcomer] was derided and subjected to cruel pranks, as happens in all communities with “conscripts” and “rookies” as well as in the initiation ceremonies of primitive peoples: and there is no doubt that life in the Lager involved a regression, leading back precisely to primitive behavior.

I highly recommend you read Levi’s The Drowned and the Saved and If This Was a Man.

Here is an excerpt from page 253-255 of "Deep Green Resistance," written by Aric McBay, Lierre Keith, and Derrick Jensen:

"If we are going to talk about survival - or about courage, for that matter - we should talk about Sobibór. Sobibór was a Nazi concentration camp built in a remote part of Poland near the German border. Brought into operation in April 1943, Sobibór received regular train loads of prisoners, almost all Jewish. Like other Nazi concentration camps, Sobibór was also a work camp, both for prisoners skilled in certain trades and for unskilled labor, such as body removal. Sobibór was not the largest concentration camp, but it ran with murderous efficiency. Records show that by October 1944 a quarter million people had been murdered there, and some argue the casualties were significantly higher.

Sobibór presented two distinct faces. Upon arrival to the camp, those selected to be killed received a polite welcoming speech from the Nazis (sometimes dressed in lab coats to project expertise and authority), and heard classical music played over the loudspeakers. The door to the extermination "showers" was decorated with flowers and a Star of David. Touches like these encouraged them to go quietly and calmly to what some surely realized was their death. In contrast, those who were selected for work were shown a more overtly violent face, suffering arbitrary beatings and sometimes killed for even the smallest failure in cooperation. As at other concentration camps, if individual prisoners even attempted to escape, other prisoners would be killed as a reprisal. (At Auschwitz it was common practice for the SS to kill ten random prisoners for each escapee.)

Sobibór is a lesson for us because it became the site of the most successful - and also the most audacious - concentration camp uprising during the entire Holocast. A small number of prisoners recognized that it was only a matter of time until they, too, were murdered, and decided that it was worth the risk of escape. However, they knew that those left behind would suffer the consequences of their act. So they hatched a bold plan to allow everyone in the camp to escape.

It was not an easy task. The camp was surrounded by multiple razor wire fences and a minefield, beyond which was forest. In addition to the SS, the camp had SS-trained guards of various Eastern European nationalities, guards who had themselves been brought in from POW camps. The perimeter of the camp had bright lighting systems and numerous machine gun towers.

A breakthrough came with the arrival of a group of Jewish-Russian POWs, with whom the long-time prisoners joined together and devised an escape plan. But to avoid being discovered, they had to keep the plan secret from all but a small group, meaning that the majority of the prisoners would be expected to escape at a moment's notice without preparation. A Russian POW leader, Alexander "Sasha" Aronowicz Pechersky, understood the benefits. "As a military man, I was aware that a surprise attack is worth a division of soldiers. If we can maintain secrecy until the last minute of the outbreak, the revolt is 80 percent accomplished. The biggest danger was deconspiration." In preparation for the escape, the conspirators used their trade skills to make or steal knives and axes small enough to conceal in their clothes.

At four o'clock on the day of the escape, they sprang into action. Carefully but quickly, they began to lure SS guards into private locations one by one, under various false pretexts. Then, small groups of prepared prisoners would quickly and quietly kill the SS men by striking them on the head with an axe, or by covering their mouths and stabbing them to death. Within an hour they had killed eleven SS men, half of the SS guards present at the time, and concealed their bodies. At five o'clock they came together for evening roll call, but they arrived slightly early, before the remaining SS men had gathered. Their plan was to avoid the minefields by simply marching as a group to the front gate, as though they were on their way to work detail. Upon reaching the gate, they had hoped to shoot the two Ukranian guards present and then rush out the front way.

Though they had been lucky so far, one of the bodies was discovered at the last moment, before they could make for the front gate. The Russian Sasha made a very brief "every man for himself" speech and encouraged everyone to escape immediately. The camp then burst into chaos, with some proceeding to the front gate, and others breaking their way through the fence and taking their chances with the mine field. All had to deal with the machine gun fire from the guard towers.

Of the roughly 550 prisoners, 150 were unwilling or unable to escape. Some were separated in a different subcamp and were out of communication, and others simply refused to run. Anyone unable or unwilling to fight or run was shot by the SS. About eighty of those who did run were killed by the mines or by hostile fire. Still, more than 300 people (mostly with no preparation) managed to escape the camp into the surrounding woodlands.

Tragically, close to half of these people were captured and executed over the following weeks because of a German dragnet. But since they would have been killed by the SS regardless, the escape was still a remarkable success."

I read Jean Francois Steiner's book Treblinka in the 80's. It covers in detail the camp of the same name in Poland.

He spent a good deal of time covering the design of the process and how they managed people to keep them under control and moving into the "showers." The pressure to have people "keep up and move along" played an important part. They could not be given the time to realize what was happening.

Worth the time read.