I spent New Year's 2011 in Cologne which is a 2.5 hours drive away from where I live.
The weather wasn't great but that did not deter the party crowd from roaming the streets. We had dinner at Cölner Hofbräu Früh, a century old brewery serving homemade beer and hearty German food. If not for drinks or dinner, it is still worth popping inside just to have a look and walk through the different rooms. According to their website they have the capacity to seat 300 people!
Close to midnight people were setting off their own fireworks around the city and along the Rhine. The resulting display was totally uncoordinated and chaotic (world's apart from the show in London that I saw on TV the next day) but it had its unique charm and was fascinating as all fireworks are. Just because we don't see them every day.
I stayed at the Pullman Cologne which is located about 1 km from the Kölner Dom, the majestic Cathedral that dominates the city's skyline. A very close to perfect stay; comfy and modern rooms, a beautiful wellness area and excellent service in all areas. The breakfast buffet was equally delightful and could not have offered anything more. Late check out until 3 pm was permitted. Definitely recommended and a great start into 2012!