I am using Carbonite (Online Backup Software | Carbonite
right now. Cost is $56/year and offers unlimited backup for one machine. If you have more than one machine, you'll have to check their enterprise offers. Initially, they do the backup in the background so as to not interrupt your work. It could take a week or longer to get it all. Afterthat, they just do incremental saves to get all your changed files. You can restore a file at anytime. You click "Restore" and you can then browse your backed up files as if you were in the Windows Explorer (My Computer). You can restore files to the same machine or any other one, say if you are away from home.
I'm not as familiar with Mozy, (Online Backup, Data Backup & Remote Backup Solutions | Mozy
) but I've heard good things about it. Pricing is similar but with 100 gigs I think you will find Carbonite is better.
You could always split up your files, some to Dropbox, some to Microsoft (they will take 25 gig free), Amazon has another 5 gig for ya. Google just announced their cloud storage. Sounds like a hassle to me, but these are all free.