I use a 28 f/2.8. Great lens. Have also used a Sigma 30 1.4, great too but it shorted something on the camera which prevented it reading any lens CPU. Have also used the 35 from Nikon but didn't like it.
These aren't wide on a crop body though, more like a standard. If you want wide then you will be looking more in the 14 and 16mm range.