I ordered a PandaBoard today. It is the next generation ARM platform from TI. It has a full gig of RAM, dual core processor and onboard wireless, among other goodies. Also, it will run the current Ubuntu, which is what SchoolTool would use on the ARM platform going forward. The SheevaPlug is a bit of a dead end in that respect.
OTOH, the PandaBoard is more expensive ($174), and that doesn't include a case, power supply, etc. I'm hoping I can make a slick display case using the laser cutter at AS220 Labs to use at demos.
It's back-ordered right now but should arrive next month sometime.