Csync2 is a cluster synchronization tool. It can be used to keep files on 
multiple hosts in a cluster in sync. Csync2 can handle complex setups with 
much more than just 2 hosts, handle file deletions and can detect 
conflicts.
   
It is expedient for HA-clusters, HPC-clusters, COWs and server farms. If 
you are looking for a tool to sync your laptop with your workstation, you 
better have a look at Unison (http://www.cis.upenn.edu/~bcpierce/unison/) 
too.

WWW: http://oss.linbit.com/csync2/