Freeduino or Roboduino. These are the Arduino clones. They are EXACTLY the same as the real thing (sometimes better) for about 1/3 - 1/2 less.
I have various freeduino and other Arduino clones that I am happy with but I would not say they are exactly the same thing as the official arduino boards, nor are the always cheaper.
The roboduino looks to be nice board with extra features but it appears to be over 50% higher in cost than the standard arduino board.