I'm not sure if this belongs here, so please point it out if there's a more appropriate sub for this.
My school will be decommissioning and throwing out lots of identical Optiplex 790 systems (i5-2400, 2x2GB DDR3, 500GB HDD) in December, and instead of letting them going to waste, the computer society (of which I am a member of) obtained permission to keep several of them for "R&D". I had the idea of linking them up together to form some sort of extremely basic supercomputer just for the fun of it, but I have no idea how practical or realistic this is. Some questions:
On a scale of ten, how practical or realistic is this? How so?
What software can be used to link the nodes up and parallelize the tasks?
Which linux distro is preferred?
Is a managed switch required?
Mod edit: removed dodgy links