SparkleShare - Sharing work made easy. Badly blogged, but this looks quite promising at first glance - a simple Git server is used. Unfortunately, it seems to be based only on SSH Git, not HTTPS, at least I don't see anything about it in the docs - HTTPS would be more universal (even if passwords would then have to be stored). What is still missing is an iOS or Android client (Android is apparently in the works), but OSX is already supported. It seems that the most activity in the open-source alternatives to Dropbox is happening here - but I'm still wondering how the server behaves with massive file additions and deletions - for example, I have the current raw photos of the last few months in my Dropbox. A "raw" Git repository grows very quickly to unimaginable sizes ... (and you probably also have to do regular packs so that changes to DNG files don't blow up the repository). One small detail on the side is still important: SparkleShare uses a public IRC server for synchronization messages - so even with self-hosting, all clients are on this server and exchange their triggers via it. Should be kept in mind, because this would be a classic attack vector (and if the IRC server fails, the self-hosted system also hangs). SparkleShare is open source, so you can certainly also plug in your own IRC server here and simply use your own packages.