I've been using Mozy for my backup needs for a few months now. Mozy is a free client that automates backups on your computer. They support Windows now with a Mac version coming soon. (Scott Pinkston blogged about the Mac client a few weeks ago.) With my Windows being down I've really had to rely on Mozy's restoration service. All you do is logon to the web site and you can then browse your stored files. Find the file you want (like a Thunderbird mail folder) and Mozy will begin the restore process. You basically just wait for an email (this took about 1-2 minutes) and you can then download the file. A few weeks back I paid for the unlimited service which is a deal at 5 bucks a month.