I've been experimenting with dotMac recently - I haven't looked at dotMac accounts since you had to pay an annual subscription - it was great when it was free! Anyway, with the addition of group pages, and a boost to 1GB storage, plus the ability of WiFile Pro on a Palm to directly connect to dotMac iDisks, I thought it was time for another look.
So far I can see a lot of potential. dotMac can provide a highly collaborative environment for education, without the limitations of institutional IT infrastructures. Coupled with wireless 3G data access (as long as the price is low)... still experimenting with this idea.