SyncBox + MyWatcher:

This one is c# ish and behaves like dropbox does.
its also forseen to be able to share files via p2p.

It uses rsync, bison, c#, mingw, cygwin, unix daemon (server)

This is really PreAlpha and not up to date.

You can use this even if you want to get along with file event handling in microsoft .net! And react with Syncprocesses (os independent)