SparkleShare - Self hosted, Secure, Instant file sync, Dropbox alternative

SparkleShare is a file sharing and collaboration app. It works just like Dropbox, and you can run it on your own server. It creates a special folder on your computer. You can add remotely hosted folders (or "projects") to this folder. These projects will be automatically kept in sync with both the host and all of your peers when someone adds, removes or edits a file.