DroppedBoxx- The Unofficial Dropbox Client For Windows Mobile. This is a beta application designed by someone who wanted this functionality.
It is still being developed so keep an eye out for new versions and features. But as of right now, I am using it to make my life easier and have full access to my files on the go. Vpn. Rsync. Ssh. HOWTO build your own open source Dropbox clone – fak3r. 14 Sep 2009 **UPDATE #4 **It's 2012, and this project is still alive, although I haven't worked on lipsync as much as I should.
I want to, and have new ideas to implement and try out in the next few months. The two way sharing is a bit hacky, and I don't like it, the installer creates a cronjob: that checks for server changes to sync back every minute - and it tries to avoid conflicts by not running if a sync the other way is happening. Yes, if you're using 2 computers at once it could get confused, but so far, it's pretty good - but something I want to improve. Open Source Database Security.