Colmillo (5553-0260, 5592-6164, 6114) was set up by expatriate Brits in a nifty house in the Reforma Centro area of town. Downstairs, there's house music and DJs are often invited. Upstairs, they often have live jazz.
You can also check out the Avant Garde (5095-3996/97) in the Condesa if you're up for some hard-core partying in a minimalist setting and with some great DJs, both local and foreign.
Another option is Rioma, a very chic nightclub/lounge located right on Insurgentes Sur in the Condesa. Beware: they're very picky at the door.
For something a little out of the ordinary, try the Pervert Lounge (5510-4454) in the Historical Center where you're guaranteed some of the best cutting-edge techno music around.
Further uptown, in the new shopping center in the heart of Bosques de las Lomas, there's Ibiza (5245-1050), while on Masaryk there's the VIP (5281-1235,2502,4461) -- both are for the wealthier, more stuck-up set.
Now if you want to have a night out dancing to Caribbean music, then a must for all salsa-lovers is Bar León (5510-3093), a very old and well-renowned bar situated by the Zocalo, right behind the cathedral.
Another very popular place is Mama Rumba, with live Cuban and local bands playing on weekends. The atmosphere is very festive and fun without being seedy. There are two Mama Rumbas, one in San Angel (5550-8099) and another in Colonia Roma (5564-6920).