It was recently announced that Polaroid will cease production on Polaroid cameras and film:
http://www.boston.com/business/technology/articles/2008/02/08/polaroid_shutting_2_mass_facilities_laying_off_150/
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:
http://www.shopping.hp.com/product/photography/camera/1/storefronts/Q8508A%2523A2L

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!