I'd recommend the Nano Series from BasicMicro.com. These are PIC processors. They come as 18-pin ($8), 28-pin ($9) and 40-pin ($11) versions, so you have a choice between cost and the number of I/O pins. The beauty part is the free(!!) BASIC designed for these, which is quite powerful. Another plus is the fact that these are bootloaders, which means you just need a PC serial port to program them. An inexpensive ($17) USB-driven programmer, using just a 3-pin header, can be had for programming, then used for serial communications when programming is done. This means, if you have some breadboarding equipment, a 5V AC adapter or adjustable power supply , and a few components already, you can be programming useful circuits for $25 and some study.
Check them out at **broken link removed**
Just a thought.