Check out Crypto.cat and install it on your server as well!
SparkleShare is a really interesting alternative to Dropbox for making your files available on several computers.
It’s only version 0.2 as of now, but take a look at the roadmap to see where the project is heading.
It’s currently available for OSX and Linux. Support for Windows, Android and iOS is planned.
Read more at SparkleShare.com.