A bit late to the party, but here are some suggestions. I'll focus on places important to the Revolution and not necessarily Cuban history as a whole.

-Palacio Presidencial. This was the Cuban versión of the White House. Batista governed from there until there was an assassination attempt that almost reached his office. Some bullet holes remain from the attack, in which the half dozen revolutionaries were killed to a man. It was the Directorio Revolucionario, and not Fidel's 26th of July Movement, but a key moment nonetheless. -University of Havana. At one street corner you can see the spot that another member of the Directorio was shot dead after proclaiming revolt by radio. -Humboldt 7. A bunch of revolutionaries were in hiding at an apartment building. Humboldt Street, number 7. A member of the PSP (Cuban Communist Party, known then as the Popular Socialist Part) ratted them out because the Communists saw them as bourgeois threats to the Party's claim on the support of the masses. All the other revolutionaries, mostly from the Directorio, were shot to death. There is a famous photo of blood trickling down the stairs and a little boy of 3 or 4 years of age staring at the blood as it pooled. -Plaza de la Revolución, which is a giant political plaza where many famous speeches were uttered by Fidel. There is a giant monument, like the Washington Monument, which you can ride to the top. -Plaza Anti-Imperialista is the plaza in front of the US embassy where Cuba does concerts and protests of US foreign policy. -Fortaleza la Cabana. It is an 18th century Spanish fort across the habour from Havana proper. It was used as a place for detainment of political prisoners after the Revolution came to power, until more permanent places were built.

Those are some of the big places to visit in Havana, at least. Remember, though, the Cuban revolution was mostly in the rest of the country. They didn't reach Havana until after coming to power. The people fighting urban guerrilla warfare in the cities were mostly people from the Directorio Revolucionario, which was a radical student organization, akin to the Weather Underground here in the US.

If you're traveling beyond Havana: -Santa Clara is where you can see relics of where Che successfully derailed the famous bulletproof train that Batista was using to transport troops and supplies from the capital to the countryside. -Santiago de Cuba is where Fidel originally gave his speech announcing victory (he didn't get to Havana until a few days later). -Cinco Palmas. If you go deep into what is today Granma province, the very definition of backwater, you can go to Cinco Palmas (five palm trees). After Fidel landed on the Granma most of his men were killed or captured and his fighting force was separated. Raul Castro led his men and Fidel the other half of the troops. They reunited in 5 Palmas after days wandering the jungle. Of the 50 some that had come less than 20 arrived at 5 palmas and less than 10 of these had rifles. Fidel supposedly said 'NOW we'll definitely win the fight'. Probably apocryphal, but it makes for a nice story. -Isla de la Juventud, previously Isla de Pinos. You can go to the island and see what's left of the Presidio Modelo, a political prison built in a way inspired by the British idea of a panopticon. Fidel was imprisoned there after failing to take the Moncada barracks. -Moncada barracks. Speaking of which, you can see the famous barracks if you go to Santiago de Cuba. This was the base Fidel attacked and failed to take in 1953.

If you want suggestions for places that are historically significant beyond the revolution, let me know.