Lense Recomendation?

I just bought my first DSLR a Rebel XT. Anyways I am trying to figure out what lens to save up for. I am looking for a good zoom lens for doing wildlife as well as some motocross and drag race photos. Is the cheaper Canon EF 75-300 III any good? What about the EF 70 300 IS ? Any other suggestion would be greatly appreciated.

Thanks

For what you want to do I'd say you are better off saving up for faster glass. If the 2.8's are too costly for you take a look at the 70-200 f/4 as a cheaper alternative.

The 75-300 is a bit too slow, but if you up the ISO, you might be alright. If there is any way for you to rent that lens, try it out.