The CMUcam has been popular with robot builders for a while. The third version of the CMU vision sensor is out and should be even more popular becase CMU has open sourced the code. The CMUcam3 is based on the ARM7TDMI with code written in C and compiled using a standard GNU gcc toolchain. The sensor provides 352x288 RGB CIF resolution, a frame rate of 26 frames per second, and a basic image manipulation library that includes image clipping, downsampling,thresholding, convolution functions, color blobs, frame differencing, and historgram generation. The CMUcam3 goes for about $240. For more technical details, see the recently released technical report from the CMU Robotics Institute titled, CMUcam3: An Open Programmable Embedded Vision Sensor (PDF format).