I’m liking Hamburger berg already.Hi there I'm from Hamburg.
Namaste already mentioned most of the important clubs. I would add DOCKS at Reeperbahn, Villa Nova at Reeperbahn, Blankenes Kiez Internat and Kurhotel at Grosse Freiheit for afterparties (each Saturday/Sunday until 12am or later).
I just want to add http://ohschonhell.de/ is the best site to find all Hamburg Clubbing dates, Afterparties and Unofficial Outdoor parties. If a party is not listed there it simply is not worth it.
By the way ohschonhell means as much as "OMG the sun is up already".
My personal favorites would be Übel&Gefährlich and Waagenbau because of the crowd and the location. But same as anywhere else it always depends on who is the party organizer.
Tächno is throws very popular parties. Search for Rich vom Dorf, C2Datei or Miyagi. All of these are very popular Hamburg DJs.
About the Bars.
There is a new bar called "clouds Heaven's" at Repperbahn located in the upper level which gives you a nice view.
Beside that many people going drinking and clubbing at a street called "Hamburger Berg" just next to the reeperbahn. There are about 10 bars which give you the original dirty and cheap feeling and turn into small clubs after 11pm on weekends. Many use them for free clubbing.
Also very popular are the bars in the "Schanzen Viertel" (Susannenstraße/Schulterblatt).
Hope this helps.
Restaurant Hala, Beselerplatz 11, lebaneseAny more tips for Hamburg? Looking for places to eat as well, go the end of April!
PerfectRestaurant Hala, Beselerplatz 11, lebanese
Neni, 25hours Hotel Altes Hafenamt, east mediterranean
Bullerei, Lagerstraße 34b, steak
Henssler Henssler, Große Elbstraße 160 , sushi
Clouds Heaven's Bar & Kitchen, Reeperbahn 1, crossover, and after dinner enjoy their rooftop bar
East Restaurant, Simon-von-Utrecht-Straße 31, sushi & steak
and a lot more