I recently got a Sigma 17-70, 2.8-4.0 telephoto to fit my Canon Rebel XTi. The lens blows the socks off the 18-55 stock lens (duh) and has a pretty incredible macro (which allows you to get mere inches away from your subject. I’ve been happy with its brightness and, though it’s a pain to carry around, the heft of the lens is nice when compared to the 50mm 1.8 or other kit lenses I’ve tried on the camera. I put a couple of photos on flickr taken with the sigma lens.