So many times I've wanted to go to an anime convention and participate in the live voice acting contests, but I don't live anywhere near one.
There's an online voice acting contest at Behind the Voice Actors where you can win a $100 prize http://www.behindthevoiceactors.com/act-your-voice-out/
It's kinda like Americal Idol. There's auditions, then performance rounds where people vote for the best. You just record your audition and submit it.