Evaluation boards are a great way of getting you up and running, letting you learn technology at a good price. So, what is an evaluation board? Wikipedia has a good answer:
A microprocessor development board is a printed circuit board containing a microprocessor and the minimal support logic needed for an engineer to become acquainted with the microprocessor on the board and to learn to program it
While some boards can be very expensive (a few hundred dollars), most are extremely cheap at only tens of dollars, sometimes even less. All evaluation boards allow users to have a close look at the microprocessor or microcontroller that powers it, and normally come with a development environment to get you up and running, and enough I/O to add your own peripherals. Once again, there is a difference between some boards; while some might have dozens of different peripherals, others might not have any at all, and require the user to add them.
The following is a list of evaluation boards that I have had (or still have!), and my impressions while testing them.