The Arduino Nano is like a miniature Arduino Duemilanove not only is it tiny, but you can stick it into a breadboard. It costs $22, which is a good price for a genuine Arduino product, but since it is open source, there are a lot of low price clones available. Here's a 3-pack on Amazon for $13. Here's a 5-pack for $19. If you only need one, you can get it for $8, which includes the cable.
