There's no shortage of vegan shopping sites on the Web, but I recently enjoyed a particularly nice browsing experience on Cosmos. They understand what vegans really want-- they actually have a separate shopping category for "vegan cheesy foods."
I love shopping on vegan web sites because first, I don't have to scrutinize every label for hidden animal products; second, I like supporting vegan companies; and third, I can shop for items I may otherwise have never encountered elsewhere.
Other highlights -- a huge selection of supplements, a gluten free area, vegan gift ideas, a books area, and clothing/accessories areas. They also feature a top 10 best seller list on the homepage, so you can see what is popular on any given day.