Dropbox

Dropbox is a free cross-platform folder synchronization service that allows users to save files to a secure folder shared among any Mac, Linux, Windows machine or even mobile device. The contents of the folder are also automatically updated and stored securely on the web. This means, rather than using a flash drive to tranport files between different machines (and risk losing it), you can quickly and automatically update information between serval different computers and even access it from the web if need be. There's a lot of potential for this in education and distance learning. It can possibly provide a way to share resources with students or allow students to collaborate in the creation of group projects.