I'm aware of the fact that Denazification most likely quelled any serious attempts at reviving National Socialism, but were there any underground movements trying start the Third Reich up again? Sure there's Neo-Nazism, I'm more curious about revival attempts from people who were actual Nazis during WWII.
Yes, there were. In the early days of the Federal Republic of Germany (West Germany or FRG) there was this guy -- Otto Ernst Remer, a former Generalmajor of the Wehrmacht who played an important role in crushing the assassination plot of July 20, 1944 (he personally arrested his superior officer Paul von Hase who was a participant in the coup attempt). In 1949, Remer and ultra-Nationalist novelist Fritz Dorls founded the Sozialistische Reichspartei ("Socialist Reich Party", abbreviated as SRP), a party openly dedicated to bring back National Socialism. The SRP referred to the Federal Republic as a puppet regime, claimed that Karl Dönitz was the last legitimate Chancellor of Germany, that National Socialism was right "in principle", and called for a unified Germany within old borders. The SRP had some pretty impressing election results in the northern German state of Niedersachsen (Lower Saxony) where the party managed to get 11% in the 1951 state parliament election. In 1952, the Bundesverfassungsgericht, the new supreme constitutional court of West Germany, banned the SRP, which was subsequently dissolved. This was the first time the BVerfG banned a political party completely (invoking article 21, paragraph 2 of the constitution called the Grundgesetz), and to this day it has only done so twice. (The other time being the prohibition of the Communist Party of Germany, the KPD, in 1956.) Thus, the story of open National Socialism in post-war Germany remained a short one.
Recently, there has been much talk about Nazi circles in Organisation Gehlen, precursor to the Bundesnachrichtendienst (BND), West Germany's foreign intelligence agency. While the service of officers with a Wehrmacht or Abwehr past in West German agencies of all sorts is nothing out of the ordinary (after all: where would all the professionals come from just a decade after WII?), the independent BND historian committee has recently been raising awareness for this darker episode of German intelligence history. Unfortunately I'm not all too familiar with the work of the UHK so I can't tell you much about this one.
