New self-hosted "Dropbox clone" (think AeroFS) BitTorrent Sync is out of private beta: http://labs.bittorrent.com/experiments/sync.html
It allows you to sync arbitrary folders, which is awesome, as well as time-limited and read-only sharing through a "secret code," which makes it REALLY nice for sharing things quickly or collaborating. I have to say, I'm digging it.
I have it set up on some of my servers and I have to say it looks awesome - It uses MUCH less memory then AeroFS (which was pig) or the DropBox client:
$ sudo python ps_mem.py | grep btsync
2.1 MiB + 169.5 KiB = 2.3 MiB btsync
And thanks to bittorrent, when you have tons of nodes up it transfers super quick.
I'd recommend trying it out!