A friend told me about this free program called "Poladroids". I just got around to trying it, and included a screen shot below. It's actually pretty realistic, and fun too! Basically you just drag your jpeg onto the polaroid camera icon. The picture will then start to develop slowly just like the old days. The only difference was that I couldn't actually shake it. With a bit of experimentation, I'm sure there are some cool, interesting things that can be done with this program. If you're interested in posting your poladroid masterpieces online, their is an entire flickr group dedicated to it.