I ordered a Raspberry Pi a while ago to tinker around with. I did not have a fully developed plan for what to do with it yet, but a fully functional computer for $35 is something that I couldn't pass up. Now that I have messed around with it for a while, I'm really starting to like the device. Eventually, it will probably make a nice media center of sorts, but 512 Mb of on-board RAM is plenty to run a modern (headless) Linux distro and plenty of useful software has been ported to the platform.
As you know, I regularly run classes in which students participate in a virtual cyber wargame. That game typically involves about a half dozen targets, serving different purposes Some of the limitations that I experienced in the past were constraints on the number of VMs that I can bring up, and the fact that I cannot give my students their own individual machines.
With Raspberry Pi's, that might change; there is really nothing wrong with provisioning one RPi per student. I'll need a cheap network switch to power them all and punch of power supplies and/or a USB port replicator that can provide enough current for the boards. They'll still be behind some form of a bastion host, so I don't have to have a top-of-the-line switch; something cheap(ish) will do just fine.
The guys over at Pwnie Express have put together a nice bundle of security software for the RPi that might just serve my purposes very well.
It is worth exploring!