OK, I think I've finally figured out how to use box.net to upload files, and I'm going to give it a shot. I created a series of images to go along with the geometric solids - you can download the file by clicking here. I printed these out, cut them up, and then laminated them using a Scotch Thermal Laminator I bought brand-spankin' new for $10 (!!) off craigslist.
To use these, the child lays the geometric solids across the top of a mat, and then matches the pictures underneath the appropriate solid:
I didn't have any kind of reference to go by when making these cards - I simply looked around Google for things that were the correct shape. I tried to find six images for each solid, but I had trouble finding that many for the triangle-based pyramid (only found two) and the ovoid (only found four). If you have any ideas for those solids, please let me know and I'll update the file and upload it again.
I hope this is useful - I'd love to hear any comments anyone has!