Any and all non-repetitive resources for learning embedded programming should go here.

I'll start us off with the obvious.

The Arduino is an extremely inexpensive microprocessor with plenty of I/O pins to do everything you'd want.
http://arduino.cc (note: They don't sell the product; you'll need to buy it from a supplier. (http://arduino.cc)
My recommendation for beginners: Buy a pair of Arduino Duemilanove microprocessors. 95% chance you'll burn one by accident.

For the more advanced user, you might want to learn more about how the arduino works by making one yourself (http://www.instructables.com/id/Build-Your-Own-Arduino/). You get the components and a breadboard and wire it up. This may even be cheaper than buying one! Though obviously less useful.

You can buy an Arduino starter kit from adafruit (http://www.adafruit.com/index.php?main_page=product_info&cPath=17&products_id=68). Not terribly expensive, either.

Ladyada is a site run by a very competent ... lady (as the name would imply). She has a huge amount of projects and kits for sale on her site (with full-picture instructions for soldering, etcetera.) More useful projects include the MintyBoost, the XBee Arduino shield, the protoshield, and the motor controller / motor shield.
http://ladyada.net