Can you recommend a great wide-angle lens?

I have a Canon xti, and I wanted to try out a wide angle lens, I was looking on the canon website but I cant tell much different between the mid prices lenses. Can you help me out as to which one would suit me best. I am just looking to start off so something in the 300-400 dollar area would be great. Also looking for one that has a good price to performance ration. Thanks all.