Here is the place I like to go to. Variety of maps a small amount of tweaking and its all good. Irony Games. Free online resources, can't be wrong. I tinker with them just a bit also in photodraw and photoshop to tweak the lay out to my tastes. But I like'em even in basic form.
Here are a couple links you might find useful. The first is to an article by Monte Cook discussing real caves and caverns. The second is a link from the first page that takes you to a very good, small cavern map (side view). I used that map in a campaign about a year ago - but the party never made it past the first area (darn it!)