I was vegan for years. While the substitutes are available now, the best solution is start changing the way you eat, because most of the subs are terrible for you (lab contrived stuff), or are simply not as satisfying as their "real" counterparts.
For cheese, Daiya is probably the best and closest approximation of cheese you'll find. If you're recently removed from cheese, you may love or hate it. Most of the tofu slice types aren't terrible in, let's say a grilled cheese, but again, they are not cheese, but cheese like.
The tofutti sour cream, cream cheese, etc. is all decent. There are some new coconut based "yogurts" etc. that are pretty tasty. Again.. The amount of stuff they have to put in to make it "yogurt like" starts to be a little concerning, when you can just find something else to eat other than yogurt.
Tofu scramble is tasty. Check out the Post Punk kitchen for some great recipes and such... If I recall, one of their books has a pretty good list of substitutions (veganomicon)
http://www.theppk.com