For music, events, bars, etc. check out Smartshanghai.com
The bar at Captain's Hostel does have a good view, but isn't that great of a crowd. Bar Rouge is a lot better, but more expensive.
For really good cocktails Constellation is alright, but El Coctel just opened and is better in both drink quality and atmosphere.
What type of nightlife are you looking for? Expensive bars with great views, 100 RMB all-you-can-drink bars...Chinese clubs where you can drink...