The first aftermarket lens I got for my 500D was a Sigma 17-70 f2.8 macro - for $250 secondhnd. Great range of focal lengths, & it can focus very close to the front element, about 200mm I think, which is great for close ups, if not true macro..& at 70 mm is equivelant to 110 in 35mm terms, so great for general purpose or travel. To be honest , when I got my 16-35 2.8, (at seven times the cost) I was vaugely dissapointed as to my eye in the centre it didn't seem to be a lot sharper. The only downside really was the noisy autofocus, sounded like mini concrete mixer at work compared to USM lenses, no complaints about the accuracy though. Sigma have since released the same lens with silent focus and vibration compensation I think, I would highly recommend any of those for a tight budget, great first step up from kit lenses.