I thought of backing up my files to some online storage for one reason: to have a backup.
Here are my findings: (check this post date, as available options and rates keep on changing and more competetive sites will keep on coming up)
Google Drive: FREE 5 GB .. can be upgraded for low fees of $2.5/month for 25 GB and of $5/month for 100 GB.
Microsoft Sky Drive: FREE 7GB. no options for paid upgrades.
Drop Box: FREE 2 GB. more space can be acquired for free by referring to friends. can be upgraded to 100GB for $10/month and can be upgraded to more size for higher fees. Drop box has been the leader since a couple of years, and had a revolutionary easy interface for sharing and working across multiple devices.
Back Blaze: Unlimited data by computer for $4/month. This belong to a bit different category. Online backup.
In my situation I have huge amount of data (>300 GB) and all I need is to put them online for a data recovery in case of my hard disk crashes. Black Blaze is the definitely the cheapest and has great reviews. So in case you are in my situation I would advise to you.