Dropbox is a free service that allows you to store your files in the cloud, giving you easy access from mulitple computers and devices. The syncing of files is effortless and incredibly helpful.
I signed up back when it first came out but have only really been using it in the last six months. It is amazing. Simple and effective and most of all free. 2GB when you sign up. The paid plans seem reasonable, but for what I use it for at the moment, unnecessary. I make use of their awesome referral scheme which gives both people 250mb free extra on signup and install. Here is my referer link http://db.tt/Y1ovFX6 (of course).
Go, sign up, change files, sync and enjoy.