During 3rd round of HackadayPrize I will do some experiments with linear drives. The main question is if "normal" threaded rods can move a CNC machine with high precision. Furthermore I will deal with discovering alternative methods of motion sensing, especially the camera sensors of optical computer mice. Let's start with a general video about linear drives that ends with a DIY printer:

Software an schematics are available on my pages:

http://homofaciens.de/technics-machines-cnc-v3-1_en_navion.htm