I keep meaning to pick up the synergy source code and improve it a bit. Things I'd like to see:
* Make it peer to peer instead of client/server, keyboard & mouse events from all peers are shared, not just the server's
* Use mDNS (e.g. Bonjour) to auto-detect nearby peers and auto-connect to known ones. Also, use some kind of authentication - you don't want random people on a public wifi to be able to get access to your clipboard because you forgot to quit your synergy client.
Alas, I haven't had the time. Maybe this summer...