Targus Battery Grip for 70 dollars.
If you need a vertical grip... that's a darn good price for a new grip. Yeah, it's a Targus, but it's actually a rather decent piece. And it's something you can pick up at a local Radio Shack. That's about half the typical price of the Canon grip, and 30 bucks cheaper than the same Targus grip from your B&Hs and Adoramas.
Me, I personally don't use a grip... but I also don't shoot Canon. If I did shoot with those Canon Rebels, I'd invest in a battery grip myself because of my large hands. Definitely worth checking out, I think...