Depends on what sort of places you like going to and how many people will be going out?
If you like trendy kind of bars there are loads at the bottom of the Bigg Market, @ Home, the attic, the appartments, Bar 55, The living Room, tokyo etc etc. The bars on the way down to the quayside (Dean Street) are OK, Marthas, The Aitkinside, theres also a lap dancing club called Blue Velvet (perfect for a stag weekend

.
The quayside bars which I would go to are the pitcher and piano, the slug and lettuce, Bar 38, the quilted camel, casa, Chase. There's also The gate complex which has a couple of night clubs and bars, Tiger Tiger, Mood are 2 of them. I haven't been clubbing for ages but from what I remember, The Attic is cool, Sea is OK, stay away from baha unless u want Wham and other shite songs ringing in your head for days. Blue bambo is ok. Tiger Tiger is good, it's got a few rooms to choose from music wise. Mood is the same that also has a couple of rooms, normally R&B and cheesy dance charty stuff.
Hope this helps, enjoy your weekend