I'm sure this has popped up on another thread somewhere. But most here will know that I enjoy playing with Microcontrollers, and by far the best hobby platform I have found is the Arduino.
Anyway, the Gameduino project is a little "sub board" based on an FPGA that provides graphics and audio output, with a similar specification to the A500 (actually the video modes are lower resolution but with better sprite hardware, and its copper is actually a full CPU)... I'm curious about FPGAs and will be seeing what it would take to increase its addressable RAM and increase the video modes...
But the reason why I bring this board up, is that it is loosely as powerful as the Amiga chipset (similar features), but is connected via an SPI interface so is CPU agnostic... It would have been nice if the Amiga had been developed like this