iOra sells a tool that will maintain two SharePoint sites in synch
(two way replication). It does this by reading changes on one
server, sending compressed changes over the WAN, and applying the
same changes to the other server through web services calls. This
means that the two sites have the same content, but they are not
identical at the database level (eg the same item will have
different GUIDs in the two environments).
It does this for WSS/SPS 2003 and also supports MOSS 2007 within
obvious limits for a beta environment.