Sponsored by 89Rock and FOX45 News, You could win an audition and a trip to Las Vegas (including some expenses :) for your band. They have all of the rules on their website.

If you want to submit directly to the American Band folks:
How to do it
Is your band eligible to try out? Check eligibility here

An application needs to be filled out. Yes, paper work. It's a good thing our English teachers and parents taught us how to write.

Once you've got everything filled out, the address to send it to is in the submission rules, and the guidelines for sending in the Video of your band, which must be on VHS or DVD. Their submission rules also require a copy of the band members drivers lisence and a SS Card, passport or birth certificate.

Source: Americanidol.com

Interesting
The Next Great American Band has a MySpace account now. It looks like some people are trying to share their music on there already:)