When I was looking at a wide angle for my 50D, I found the Tokina 12-24 f/4 (first version) for $400. I think that would be a good option for you. The second version sells for $500, while the Tokina 11-16 f/2.8 retails for $600 (although it's hard to find at retail price). I can't necessarily suggest that particular lens, though, as I had a major issue with the first copy I received (although it produced some great images when it focused correctly). I'll have to report back after I get the second copy (should get here soon).