at 24mm there is the canon tse, an olympus pc lens and the new nikkon.
the olympus is apparently very good but hard to find and therefore expensive but can work on the canon body with an adapter.
the nikon no one knows about yet but is bound to be good looking at the new nikon 14-24m lens. but again adapters for these newer nikon lenses on eos bodies are currently in production.
the canon tse...certainly not the sharpest tool in the box but...it works, does not cost an arm and a leg used, requires no adapters, can usually be sold for the same you bought it if need be...so its not perfect but if you're stuck with / needing to shoot 35mm dslr and need a wide shift lens for canon...it does the job.
at 28mm there are as well as the schneider a couple of nikon 28mm PC lenses that can be used on eos bodies with an adaptor..I tried one once...it worked very well but...I preferred having the wider 24mm in my bag, especially here in the cramped UK.
Marc