Arq4 is online backup software and it can be used to backup to essentially rented storage space on Amazon's S3 servers.
http://www.haystacksoftware.com/arq/
http://aws.amazon.com/s3/
Thank you for filling in. I was previously using Backblaze (unlimited backup for 5$/month), but I've read somewhere that it does a less than perfect job at maintaing the all the files metadata. Hence I switched.