I would assume then, that you also have the kit lens that usually comes with the camera (EF-S 18-55 F3.5-5.6)?
Getting a lens that is significantly wider than this...probably won't be too cheap. There is the Canon EF-S 10-22mm f/3.5-4.5 USM and similar lenses (12-24), from Sigma Tamron or Tokina.
If you want a lens that is just as wide as the kit lens...but better quality...there are several options...starting around $400 and going up from there.
If you just want a lens with great optical quality and a low price...look at a Prime (non zoom) lens. The 50mm F1.8 is less than $100 US and gives great optical quality (although build quality is less than great). The wide maximum aperture is wonderful to have.