It really depends on what you need to do with it once it's in "the cloud".
http://www.edgecast.com/ <--- cheaper than Amazon S3
http://www.backblaze.com/online-backup-performance.html <--- Truly unlimited for $5 a month, but you have to keep a local copy as well, because it maintains a backup of your entire PC (no network shares...) minus the OS. But if you have 12 HDD's attached to your PC, it will back them all up. The thing with backblaze is that it's a backup for you to access, not everyone else, so it won't "serve" your files to the public.