Like Dolla said, Broad Ripple has a good bar scene. Mass Ave and Fountain Square are really good night spots closer to downtown.
Are you actually staying downtown, or somewhere on the periphery? That might help in thinking of some options.
ETA: The Indianapolis Indians (Pirates' AAA affiliate) are in town this weekend, and Victory Field is a pretty nice stadium. It's close to the NCAA Hall of Champions, Indiana State Museum, and the Eiteljorg Museum, so those could be some options downtown.
This post was edited on 7/11 at 9:42 pm