I've just bought a SonicWall SSL VPN 4200. Basically a web interface, you log in with your AD username and password and then you get access to what ever shares the sys admin feels you should.
However just to be honest, the 4200 is the bottom of the rance model and might not be usefull in a school your size as it is rated for 50 concurrent connnections and is relatively basic in terms of it's features. The recommended model (when I talked to Sonic Wall) was much more expense. It does however have a number of very good features to protect your network and the data on it and if I had the cash I would have gone for it.
We decided to go for the lower model as I am anticipating (or should that be hoping) for a slow uptake in it's use plus I can't predict how many concurrnet connections I am likely to have.
Bringing this one back from the dead, does anyone have any experience with openvpn.net? sounds like a good idea but im a bit of a miss atm to know how to use it, will have some time after easter to probably work on it but wanted opinions first.