If you have old computers in your school, or have one with a lot of memory that can support virtual machines with a free virtualization platform like VirtualBox, Turnkey Linux @ http://www.turnkeylinux.org has a vast library of “turnkey” appliances: softwares that make installation and configuration a breeze for anyone with admin access to a computer.
http://www.turnkeylinux.org/mahara: digital portfolio platform w/ social networking features. Great for faculty and students alike. Useful for transition services, IEP implementation.
http://www.turnkeylinux.org/statusnet: microblogging for inside a campus. Useful for teaching precision and concision, net citizenship, audience awareness and rhetoric.
http://www.turnkeylinux.org/elgg: social networking for campus - again, training for real world citizenship in the digital ages. Restrict to campus.
http://www.turnkeylinux.org/etherpad: we use for real time collaboration in meetings and composition classes.
http://www.turnkeylinux.org/ for the full catalog of turnkey appliances. There’s a lot of wiki options if you want to encourage authentic writing.