My favorite Kevin Smith movie (and possibly favorite movie of all time) is Clerks. I worked retail as a teenager, so I really identify with it. Same with Mallrats, though I think that spoke to most of us slackers. I don't see why it got such a bad rap, it was genuinely funny.
Jay and Silent Bob is kind of a nice big inside joke for all of his fans, and a bunch of dick and fart humor for the American Pie generation.
Then there are the two more "Serious" movies, Chasing Amy and Dogma. I found Chasing Amy to be lacking in some of the qualities that make the rest of the movies great to me (junvenile humor maybe) but it's still a good flick.
Dogma.....I have to say, I don't really "get" religion, so I don't know whether this was educational, or over my head...but I liked it.
There are more movies, Check out viewaskew.com I think it may be to your liking.