Sam - I have a Canon 28-135 f3.5-5.6 IS lens that I am kind of half-assedly selling. I got it with my 50D but I have plenty of other lenses I use more frequently so I can part with it. The IS will help you with the action stuff. It will give you greater range than the 18-55 you already have and the image quality will be improved as well.
Most of the websites are selling them for ~$400 but I am only looking to get $275 for it. I already bought a UV filter for it. I took about 10 shots with it and it's a great lens so far but I gots too many as it is...
Reviews and info here (seems to be a pretty highly regarded "next step" lens):
http://www.fredmiranda.com/reviews/s...&cat=27&page=2
Give me a call if you want to come by and check it out.