Valid from now until Friday, November 6th, you can get Guitar Hero 3 for the PS2 or XBox 360 for just $20 at Family Dollar! This includes the guitar and game! You can also get High School Musical 3 Dance Mat for the PS2 for $10.
Go HERE to find a Family Dollar store near you (and you can see the ad here as well). You may want to call ahead of time to have them hold one or to see if they still have it available.