Check out Poladroid.net.
NOTE: Currently they only have a download for Mac, but a PC version should be available later this month. I'll keep you updated.
When you download the program, a little Polaroid camera appears on your desktop. You simply drag a photo into the camera, and out pops a Polaroid. You actually have to wait while the photo develops before your eyes, and you can save it at any point during the development process.
I think someone could come up with a really cool Christmas card using this program!
Here's the normal picture:
Don't they look like they're from back in the day?