SpiderOak
Secure automatic online backup & sync, 2GB per month free
SpiderOak provides an easy, secure and consolidated free online backup, storage, access, sharing & sync* tool for Windows, Mac OS X, and GNU/Linux (Ubuntu & Debian).
Access all your data in one de-duplicated location
Preserve all historical versions & deleted files
Share folders instantly in web ShareRooms w / RSS
Configurable and secure automatic backup
Retrieve files from any internet-connected device
Comprehensive 'zero-knowledge' data encryption
2 GBs Free / $10 per 100 GBs / Unlimited devices
Required OS: 10.5
Tags:
secure
, sharing
, storage
, windows
, gnulinux
, mac
, backup



2 Opinions
SpiderOak uses encrypted cloud storage and client-side encryption key creation, so even employees of SpiderOak cannot access user's information.
SpiderOak is not quite FOSS yet, see https://spideroak.com/faq/why_isnt_spideroak_open_source_yet_when_will_it_be for more info. They've managed to release a whole range of their tools as open source though ( https://spideroak.com/code ) =D