I read about a free downloadable program many months ago on several different blogs. I starred in my reader and finally found it again the other day. Check out Poladroid for making any image look like an old Polaroid shot. And the interface is the cutest! If I was really ambitious I would take a video to show you the process, but I'm not. Take my word for it.
Here are a few shots I transformed:
You can change settings to make it more look older or more rustic and you can capture the image at any point in the "development" stage.