After experimenting with a single Raspberry Pi, I came to the conclusion that the units form a cost-effective platform to give undergrad students a dedicated Linux node for the duration for a semester. They'll have full superuser access in an isolated playground, and they can access the machine whenever they feel the need to do so.
To take a simplistic view of this, I'll need to solve two problems: hardware and software. Hardware appeared to be easy. Simply order however many units you need, find something to mount them on and power them up, and tie everything in to a network switch. It turned out to be a little more problematic than that, but none of the things that I ran into proved to be insurmountable.
I started out with ordering 15 boards, and they came in a nice small package.
For my project, I was able to get the Model B Raspberry Pi's that come with 512 MB main memory and
with on-board 100 Mb/s network jacks. Earlier in December, MCM electronics had plenty of Pi's in stock and was able to get them out quickly. If you're looking for a Pi and cannot find any, it is worth checking them out.
Next: mounting the RPi's