All Canon SLRs are compatible with their EF mount lenses. This includes the coveted 'L'-glass which is their
luxury or professional glass. They feature much more solid build quality, they're durable as hell, many of them water-sealed (this doesn't help on much beyond the 1D series bodies, though), they autofucus incredibly fast and they mostly very heavy. One very good general walk-around L (the 17-40mm) is priced at $700 which is incredible for the type of glass you get.
The 1.6-factor crop-sensor cameras (xxD and xxxD, except the 10D) will also accept their EF-S mount. The EF-S lenses will not work on the 5D, or the 1D series. The EF-S lenses, by and large, are consumer to high-end consumer lenses. They vary in quality but the range has some exceptional lenses. They have a lot of plastic in the builds so they're not as durable. Of the EF-S, I've heard good things about the 17-55MM 2.8 IS, the 10-20mm and the 60mm Macro.
Beyond their kit lenses, most Canon lenses range from decent performer to amazing lens. Other brands to consider are Sigma, Tokina and Tamron. I can't comment first-hand on the latter three, but I do know people who use Simga and Tamron glass and are happy with their results.
Personally, I would hestitate buying something that encompases such a long range such as 18-200. Especially in a consumer grade lens, you're going to find that the ends generally have to give a lot in terms of image quality for a lens to encompass that same range.
You can view Canon's entire linup of lenses here:
Canon EOS SLR Camera Systems
Most searches on Amazon will give you plenty of reviews of each of those lenses.