“Dropbox is a Web-based file hosting service operated by Dropbox, Inc. which uses cloud computing to enable users to store and share files and folders with others across the Internet using file synchronization.
There are both free and paid services, each with varying options. In comparison to similar services, Dropbox offers a relatively large number of user clients across a variety of desktop and mobile operating systems. There are a total of 10 clients, including versions for Microsoft Windows, Mac OS X, and Linux (official and unofficial), as well as versions for mobile devices, such as the iPhone, iPad, Android, and BlackBerry, and a web-based client for when no local client is installed. Dropbox uses the Freemium financial model and its free service provides 2 GB of free online storage. The service’s major competitors are Box.net, Sugarsync, Mozy and ZumoDrive.”
All new accounts come with 2GB. If you integrate Dropbox with Twitter and Facebook, you get an extra 768MB of free storage storage space.