A couple of weeks ago I saw a nice image special effect in a book about Photoshop Elements, so I came home and worked out how to reproduce it using RMagick. It's called The Polaroid Effect. I wrote a short article about it: http://rmagick.rubyforge.org/Polaroid/polaroid.rb.
If you're interested about using RMagick for more than just making thumbnails, give it a read. I hope you like it!