A friend of mine on another board showed me this site:
Some dude in Canada made it. Basically, you feed it a location and mile radius and the site culls data from musician's myspace calendars for the range you set. Basically, it tells you about all of the concerts playing in, say, Indianapolis that day, from the smallest coffee shop to the largest arena. Brilliant.
A sure bookmark for any local music lover.
I promise that I have zero connection to the people that run the site (I know spam rules are strict here). But I am a big supporter of local music, and this is a good tool if you want to support it, too.