The Testaccio district is the place to go for clubbing. There is a street lined with nightclubs and it's filled with locals and tourists. Of the ones I saw, Coyote was my favorite. For many, there is no cover charge but I'm not sure how much drinks cost because the one time that I drank something, a guy bought it for me. Sometimes you'll also see buskers putting on a show outside the clubs.
If you're a girl, be careful because there are a lot of sleazy guys there. Usually, they'll try to get your attention by asking for a cigarette or a light for their cigarette, then if you actually respond (even if you say no) you'll have a hard time getting rid of them even if you say you have a boyfriend.
Dress Code: I don't think there is a set dress code but most people wear funky clubbing clothes. One of the clubs has an alternative crowd so they've mostly got black goth clothes and face piercings. I wore a little black dress and cute wedge sandals and I fit in with the crowds.
Plenty of dance/music clubs....so good I can't remember any of the details (sorry). Only worth experiencing if you have extra time to spare. the best part is picking-up food to eat on the return journey home.
In the summer, i heard much of the nitelife moves to the beaches (?)
Dress Code: sexy
The area of Testaccio is one of the most genuinely Roman you can find. It is populated by AC Roma supporters, and its lively streets are full of words shouted in "Romanesco", the local dialect.
Testaccio has an interesting market, a nice church and a few good shops, but above all it is one of the dining and dancing centres of Rome, especially in the winter.
Dress Code: Varies a lot, but never too uptight.
Testaccio is a big popular quarter of Rome, south west downtown, and there's a street there where you can find plenty of clubs of all kinds of music: rock, house, latino. It's all in this street, one place aside the other. For all tastes!
Dress Code: Anything
A great place, plenty of locals "for Romans", usually quite cheap and/or alternative. There are also some very good but small theatres and cinemas and during summer it is a must for live concerts.
One of my favorite locals is the Radio Londra Café in Via Monte Testaccio, 65b... with live music and a good choice of drinks and food.
Dress Code: Extremely casual.. :)
Testaccio is one of the best places for music and dancing. There is literally a street that is full of just clubs with all kinds of different types of music, dancing, and other interests. Taxi is the best way to get there and all taxi drivers know Testaccio!