a service called Dropbox, which is for online back-up, synchronisation, and file sharing. They give you a small application that you install, and 2 gigs of disk space on their servers. This can be increased all the way up to 100GB if you pay a monthly or yearly fee, but the 2GB is totally free.
You copy files into a Dropbox folder which is created on any PC on which you install the application. Once a file is copied there, it automatically gets uploaded to the Dropbox server. So it's a bit like having your own virtual thumb drive anywhere you go. If you have documents in there that you change, Dropbox is smart enough to synchronise only the changed bit, thus minimising bandwidth usage.
You can create shared folders, so Dropbox users can exchange files with one another. You also have a public folder. It is possible to get a link to any file in your public folder, which you can give to friends, even those who are not Dropbox users. So it's a very simple way to share files.
Finally, even if you don't have the client installed on a PC, you can log in with any browser, and view or download your files. This is great if you have a mobile device, for instance, and want to get at your content while on the move. The link is:https://www.getdropbox.com/