If you want to remove all doubt, only buy Canon lenses. Among the Canon lenses, any EF or EF-S lens will work with your camera. EF-s lenses are specifically designed for EOS Digital Rebel and XXD series cameras where as EF lenses work on ALL EOS cameras, including full-frame digital and 35mm film cameras.
The cheapest lens you can buy is the EF 50mm f/1.8 at around $100 but, it's actually a very sharp and fast lens that is great for indoor photography without a flash. The downside is it is a "prime" lens, one of fixed focal length. Still, it's a very handy lens at times.
The original kit lens for your camera was an 18-55mm zoom, probably the EF-s 18-55mm f/3.5-5.6. If you broke this lens and just want to replace it, the new version is called the EF-s 18-55mm f/3.5-5.6 IS. The new version is sharper and adds optical image stabilization. The cost is around $140.
Two other options worth considering, if your budget allows, are the EF-s 17-85mm f/4-5.6 IS USM ($450) and the EF-s 18-200mm f/3.5-5.6 IS($600). The 17-85mm lens is better built and sharper than either of the 18-55mm lenses and offers a wider (5x) zoom range that you may find more useful. The 18-200mm is an 11.1x "super-zoom" that gives you a wide-angle to telephoto zoom all in one lens. Both lenses are image stabilized lenses which means they are designed to compensate for camera shake
One of the best online sources for info on these lenses is http://www.the-digital-picture.com. There are seperate sections for EF and EF-s lenses as well as sample photos taken with many of the lenses. KenRockwell.com also has some info on Canon lenses. However, because he's primarily a Nikon and Leica person, he doesn't cover Canon nearly as extensively as the brands he appear to prefer.