Basic Maps is a product that I have for sale at RPGNow.com for $2.30. It's just what it says it is--basic dungeon maps, 39 to be exact. For your viewing pleasure, below you can peruse all 39 of them in low res.
The first 30 are cave and cavern complexes. The last 9, which are hand-drawn and in a different style from the first group, are of an assortment of types of locations.
Personally, I think that 39 maps for $2.30 is a pretty good deal. Perhaps, you'll agree.