My ex-yearbook advisor has asked me a few times to take photos for her with her new Rebel XT. However, she has the default (35-80mm I think) lens. The pictures have been at sporting events, me taking photos of her granddaugther. I think a telephoto lens would do wonders at getting better photos. Does anyone have any thoughts on lens that are not too expensive that would do a good job? I have much to learn about photography before I go and pick out lenses myself.