Automatic Thumbnail Generating Script

Hello, I'm looking for a script that will resizes larger images in one folder and save thumbnail versions into a another folder. Many of the images are animated GIFs so this must be able to work with animations. If you've done something like this in the past, or have a ready made script please send me the URL where I can see it. If you have any questions, please feel free to ask. Also, if you're good with php & javascript I will probably have more projects for you in the immediate future. Thanks.