In the quest for cheap LIDAR I found there are quite a few <$100 units on ebay. They're used and designed for the Neato robotic vacuum cleaners.
Here is an example - http://www.ebay.com/itm/Neato-BotVac-Lidar-Distance-Sensor-Original-Factory-Part-65-70E-75-80-85-D/253168956088
It looks similar to the unit here - http://www.robotshop.com/en/rplidar-a1m8-360-degree-laser-scanner-development-kit.html
Also appears to be serial - https://xv11hacking.wikispaces.com/LIDAR+Sensor
I'm mostly looking to just play around, if it will fit on an AB maybe drive around. If everything goes well possibly put it on my rover. Does anyone have experience with this LIDAR unit?