"Dropbox is my number one productivity tool that I use every single day, both for teaching and personal purposes. If you are still toting around USB thumb-drives and moving files from your home and work computers that way, keep on reading. If not, feel free to check out some of my more advanced Dropbox articles listed below.
For the completely uninitiated, Dropbox is a cloud storage solution that is free for the everyday user. Dropbox will give you (a rather paltry) 2GB of space when you first sign up. You can increase your free space to up to 19GB by doing certain tasks (referrals will net you an extra 500MB each). If you find that you need extra space, you can opt to purchase additional storage of up to 500GB total."
Via John Evans