The Bakery has a new helper posted today for those working with images in their applications that need to resize and cache them easily.
This helper resizes an image on the fly and places it in an image cache directory for later use. Make sure your imagecache directory is writable. Future editions could include a cropping function.
The full code of the class is provided in both a cut and paste-able format and for download. There's an example of the sample usage included as well.