Dropbox has become an essential application on my system ever since I first tried it more than two years ago. If you're unfamiliar with it, it's a cross-platform tool that acts like a regular folder on your machine and runs quietly in the background. You can manage files within this folder just like elsewhere on your machine (add, edit, copy, and delete) and changes will be synced in real time between all other computers on which you are running the software.
That alone makes it invaluable for my daily computing needs, but with a little ingenuity you can use Dropbox to do much more like autostarting torrent downloads from any location or device, sending and receiving files, or synchronizing application data on applications that don't even have that functionality. Read more at TechSpot.