Everyone should be using dropbox. Its the best way to back up your important data. No excuses for loosing your soooooo important Literacy and numeracy data now ;-)
From a student point of view... Most should and would be using google docs for any finished work but because they have an email account they might want to set a drop box account up to save any personal data etc
If you are a teacher and want to keep your finger on the pulse of whats going on globally in education or even locally. Get tweeting. This blog posts explains twitter for educators and why its import to develop a Personal learning network