The Jasper is the latest 360 motherboard. It is the fourth revision of the board.
Xenon - first board - NO HDMI, 90nm CPU, 90nm GPU, often had a small GPU heatsink, and was very prone to Red-Ring-of-Death failures
Zephyr - second board - First HDMI board, still 90nm CPU, 90nm GPU, often had a larger GPU heatsink, but still using the 90nm chips, was still prone to Red-Ring-of-Death issues
Falcon - third board - First board to use a new CPU, a 65nm one, still used a 90nm GPU. Less prone to RRoD, uses only 14A on the 12v line and comes with a 175W power brick as opposed to the older 203W ones that shipped with earlier models
Jasper - fourth and current board - Uses both 65nm CPU and 65nm GPU to reduce heat, greatly reduced RRoD risk, uses only 12A on the 12V line and comes with a 150W power brick