This is a thread who's time has come...
Introducing Timbre. Enter a location or use your current location to see what live music is nearby, up to 50 miles away. Can play sample music for each band. iPhone only at the moment, and free!
http://www.timbreapp.com/ (http://www.timbreapp.com/)
TIMBRE on Vimeo (http://vimeo.com/47487347)
I'm a big fan of Songkick. It's free also. It tells you where and when everyone in your music library is playing a show. You can also find out about every show on any particular day in whatever city you want.
It is an app. Info also at: www.songkick.com (http://www.songkick.com)
I've been using soundkick for over a year now and love it. It helps me keep track of shows.
Or songkick , whatever it's called.