I'm picking up a 40D soon and I want to get some suggestions on a good lens to go with it. If I was super-duper-ballin' like that I'd pick up a 70-200 f/2.8 IS L, but unfortunately it's a bit too far out of my price range, ha. I plan on using it largely for motorsports, mostly to get decent pics @ Turner and Gresham and FD when it rolls around. I'd like to spend less than $300 if possible.

Does anyone have suggestions?