In case you missed them, ETC-Press has a beautiful collection of 3-part cards that you can download for free here (special thanks to Lisa from the montessorimakers yahoo! group for mentioning them).
There are 3-part nomenclature cards for land formations, geometric solids, cloud formations, phases of the moon, the solar system, parts of a flag, parts of a leaf, parts of a tree, world continents and hemispheres, and world oceans.
In case the link above doesn't get you to just the right spot, click on "Free Materials" on the left-hand side, and 11 items should come up. Once you've selected an item, you'll see the words "click here to download the file" in teeny-tiny print underneath the item's description. Look closely - I missed it the first time through.