Put as many ideas/options out there, that's good. Of course a very simple & cheap solution imo is to use old machines, breath new life into them via Damn Small or Puppy Linux.
Otherwise, there are myriad full desktop solutions 200-300$, and thin clients >$200 by Icop and Norhtec, to name a few...
http://www.norhtec.com/
http://www.icoptech.com/ebox-pc/ »