This Nightlife Guide is understandably Ironbound heavy, but did mention Swahili Village which is a popular place and one of my preferred spots. It's usually crowded, at least on the bar side, from Thursday on. Bar Vanquish on Market Street also gets a good crowd on weekends. Lit 21 can get crowded depending on the party. The last couple times I've been they did a poor job with space allocation though. They opened up every area but only have enough people to fill one, so the place seems empty although there are a decent number of people there.

I stumbled into a party going on at bunkr on Halsey Street last night which was cool.

And, though not NightLife, Blueprint cafe has a DJ on Saturday. That place is a cool hangout and great food, especially for brunch (closed on Sundays I believe.)