Siebe Warmoeskerken wrote a well illustrated tutorial on turning digital photos into film in the blog of De Vetpan Studios. He uses Exposure to do most of the heavy lifting, but also shows some useful Photoshop techniques. The visitor comments at the bottom of the article are full of praise and I completely agree.
I recommend watching the video at the highest resolution in full screen mode.
Here is another article on using Exposure in the same blog. This one shows a little more variety of effects.
Here is the video that goes with it.