The area close to Nollendorfplatz is the old West Berlin gay area. There are some bars on the corner Fuggerstraße/Eisenacher Str. where you will find a lot of men/boys offering their time for your money. But most of the bars are not like that. My favourites in the area are 'Hafen' and 'Heile Welt', both in Motzstraße.

An other area is in the Prenzlauer Berg (East Berlin)

The best clubs I think are Schwuz (close to U-Mehringdamm) Schwuz-Club in Kreuzberg and the GMF GMF in Cafe Moskau (former east).