BT Sync is AWESOME! Free (if you've got a friend or two), although you can also use it to push files around your own machines if you've got multiple.
Install it on one machine and point it at a directory or two. You'll get a "secret" - essentially a long string of characters. Install it on another machine somewhere else (remember that friend?) and use the "secret" from the earlier step. Presto! All of your data starts copying across the internet. Bandwidth usage is configurable. You can install on multiple machines for multiple backups.
Runs in one of two modes "sync" or "read-only". In sync mode, if a file is changed on EITHER (or - if multiple - any) machine, it changes on all. Delete a file, it deletes on all. This is the best mode for keeping a folder in sync across multiple machines, like "My Documents" on a laptop and a desktop. The "read-only" mode means that one machine pushes changes, and the other can only get them (but not push changes back).
It also comes with Android, iOS, Mac, and NAS versions. On my phone, when I take a picture, it's backed up immediately at full quality back at home. My next step is to install copies on my distant relatives' computers and make a read-only backup on my machine.