Canon Zoom Wide Angle-Telephoto EF 28-135mm f/3.5-5.6 IS Image Stabilizer USM Autofocus Lens

So you have a shiny new SLR, (or at least, a new-to-you SLR) and you need a lens. I've recommended this lens to many people due to its solid performance across a wide range and the image stabilization. Plus, it's quite affordable. I swap lenses all the time and it really is quite a hassle. This lens is great for backyard picnics, where you'll be both close and far from your subjects in a medium-size environment. I brought this to the zoo once and it just didn't have the reach to fill an animal in the frame, even with the 1.6x crop factor. However, I noticed it was perfect for photographing the parents and kids around me! As it got darker, the IS worked quite well.

If you're going to get just ONE lens, I highly recommend this lens if you have a Canon 10D or earlier. If you have a Rebel, Rebel XT, or 20D and you want to compensate for the 1.6x crop, the Canon EF-S 17-85mm f/4-5.6 IS is the alternative. I would have gone for this option, but I was seeking a lens for my Canon 10D, which cannot use EF-S lenses.