Syncplicity is a great service. They provide hosted disk space, access via the web, and a Windows program that automatically synchronizes the versions of the files you select on your computer with the files stored on their servers. In fact, if you have 2 computers (for example one at home and one at work), Syncplicity can synchronize your files between all three places. But wait - there's more! You can also share the files you want to share by providing friends with url's to them.
You can get a free account that gives you 5GB of space on their servers; you can get 50GB for $10/month or $100/year; or you can get 100GB for $20/month or $200/year.
(Oh, and if you let me send you an invitation, I'll get another 1GB)
This is a great painless backup solution. Try it!