[blazingice]

I've had a good experience with the Canon 28-135mm f/3.5-5.6 IS USM. It's right in the middle of your price range and has image stabilization and a good zoom range. It's my go-to lens if I'm traveling light.

If you can possibly save up for the 24-105 f/4L, do it.

Everyone else suggests that you get a prime lens - they're fantastic for portraits but so so very annoying in any other situation. On the plus side, the 50mm 1.8 Canon lens is amazingly cheap and light. On the downside, it's noisy, takes forever to focus, and it's just not very versatile. I'd get it after a good zoom lens; it's worth having but not right off the bat.

The right lens for you really depends on your photographic style - if you shoot wildlife, scenery, street photography, or people, your lens choice will be wildly different.

Cheers!

P.S. my go-to site for lens information is http://www.canonlensreview.com - it's quite good and simple.