SpiderOak
SpiderOak automatically encrypts files before uploading them to the server.
SpiderOak Hive works a lot like Dropbox, minus the NSA partnership. Anything you add or edit within the Hive folder is automatically backed up, assuming you're online, and will sync with all your devices.
also: SpiderOak: Encryption under the light of PRISM revelations
This looks pretty good. Is it just as easy to use as Dropbox? Any other pros/cons?