Between 18th street and 20th street and Blake and Market. There are a few places down there that play hip hop. One of my favorites is LoDo's - it's on 19th and Market. It's 2 stories and has a roof top bar for when it gets really hot.
Don't waste your time:
Bash - Great music, but it is ghetto! I've slashed my foot on a piece of broken glass in the bathroom and there are ALWAYS fights and creepy guys.
Jacksons - Really fun to chill on the roof and watch a game and have some beer with friends, but they advertise themselves as a club, but no one is ever there.
Market street is fun and a good place to start - but be sure and leave early if you want a cab before 6am. If you are driving, there is a lot at 18th and market where I always park because to the north are all of the hip hop clubs and to the south are the "hook-up" trendy martini bars so you can go where the night takes you :)
Have fun - Denver is a blast!

