It was recently announced that Polaroid will cease production on Polaroid cameras and film:
If you’re planning on using anything like this for your wedding guest book, be sure to order now!
The company is making film to last till next year, and I predict that you’ll be able to only find this at resources such as eBay moving forward.

Still love the Polaroid look? Consider a digital camera, docking station and quick printer, like:

I think it will be pretty funny, a generation or two from now, when we’re at our kid’s weddings and they will have no idea what “shake it like a polaroid picture” means!