Lots of people own several computers. Not to mention different operating systems.
Don't you wish you had a folder with some files that will be accessible from every single one of your PCs ?
A friend of mine recommended Dropbox (www.getdropbox.com)
This is a software, compatible with Windows, Linux and Mac, which creates a folder on your PC(/mac), that is linked to your account, and with every computer that runs the program (with the specific account) - This folder will be in complete sync.
If you need it from a shared pc - you also have a web interface to download your files.
Also, a public folder is created which you can just send a direct link for your file to a friend
You get 2GB of online storage for this matter - completely for free from Dropbox, and you can also revert to earlier versions of your files.
Dropbox claims to be encrypted - but I can't guarantee it, so I wouldn't recommend using it for sensitive data (passwords, etc.)
I started using it. Definately recommend it!