I have been using this utility for about 6 months now and I am VERY impressed.
DSynchronize
Basically, you can set up any pair of folders or drives (incl CD/DVD drives, FTP) on a network to stay in sync with each other. Uni or Bi directional, Realtime, Scheduled, On demand, Auto start etc etc.
And its a tiny 100kb application (smaller than some web pages). Hasnt missed a beat for me.