This weekend I saw Microsoft's SkyDrive and thought that was pretty cool. 25GB of free storage, where each folder can be set with different permissions . . . that's all right! I could see sending my teachers and students that direction.
But then today I saw drop.io, and I am very impressed. You share files up to 100MB in each drop, but the flexibility is what takes my breath away--is there a mode of communication it doesn't work with? I'm going to see what a group of students with cell phones can do to make it a collaborative sharepoint.