Darren wrote this at 1:32 pm:
If you shoot with a small-sensor digital SLR (often called “APS-C” sensors) such as the Canon 10D/20D/300D/350D or Nikon D70/D100/D50, you’ve probably already been frustrated by the difficulty of shooting wide angle.
All these cameras have a 1.5x or 1.6x ‘crop factor’ due to the smaller sensor, so your 24mm lens has a field of view equivalent to a 36mm or 38mm lens on a film camera. It’s nice for the bird photographers working at the long end (cheap 300mm lenses become 480mm!), but it sucks for landscape photographers working at the wide end.
Photo.net has a roundup of ultrawide zooms for Canon and Nikon DSLRs that might help you choose a suitable new lens. Although they don’t review each lens, at least it’ll help you figure out what the options are and you can then Google for technical reviews of those lenses that appeal to you.