Joe Lencioni over at Shifting Pixel, has written a post about the easy to use image resizing script. It’s a really simple script that you use by specifying the parameters in the src part of the img tag.

The major advantage of this script is that it allows me to resize and crop any image on my website without touching the actual image or writing any code.

Try the script yourself, and if you can improve on it let him know by leaving him a comment.
A ridiculously easy-to-use PHP script for resizing images the smart way.