I've used Last.fm for a couple of years now, logging (or, in their terminology, "scrobbling") over 58,000 tracks as I listen to them. It's kind of your music player's "most played" list on steroids, as it's cross-compatible with everything.
Last.fm also works with local event listings, as well; they've just released a new app called "Festivals" that will hopefully find its way to music fans' phones everywhere.
Festivals works like a trip planner to make sure you get the most out of your festival experience. It provides you with a list of shows that are occurring during the day, as well as matching your compatible tastes according to your Last.fm account. It really serves your interest to be using the service beforehand, as the more music you record to a profile, the more refined your music compatibility will be.
While using the app, you can make an itinerary of where you're going to be, read bios of the bands that are performing, search for specific appearances, and see what your friends using the service are doing, as well.
While I can't see myself using this app on a regular basis, I think it's a great alternative to festival-exclusive applications; if you're anything like me, you hate clutter on your phone. It should be worth noting, however, that this app is only available for American users, and won't be compatible anywhere else.
It is free, though, so if you're looking to do any major concert-going this summer, I'd give it a download.