For vegan casual and athletic shoes, there are plenty of options (such as many of the New Balance styles).
For men's dress shoes, though, it is a lot harder to find non-leather choices. I was happy to find some snazzy, all man-made material shoes at Rack Room in Cary yesterday: Borelli Mason shoes.
They are pretty nice looking, reasonably comfortable, and - hey - cheap too! I particularly like the brown ones.
Also, see the posts about women's shoes here and here.