Dropbox is according to Wikipedia:

Dropbox is a Web-based file hosting service operated by Dropbox, Inc. that uses cloud computing to enable users to store and share files and folders with others across the Internet using file synchronization. It was founded in 2007 by Drew Houston and Arash Ferdowsi as a Y Combinator startup.

It is really useful, at it has clients for iPhones, Blackberries, Android and others, as well as Windows and Macs, so Debian is a must.

How to install Dropbox in Debian Linux

Thanks to my friend Raphael Hertzog, we now have Debian dropbox packages.

So, if you need to install it on your Debian, check this page