Bucardo is a mature replication system written in Perl for PostgreSQL that supports asynchronous replication for both master-slave and multi-master systems. Originally designed for slow and unreliable networks, it has remarkable recovery ability, an easy to use command-line interface and development is active! Uses for Bucardo include: a slave read-only database, multi-master replication, data warehousing and just having fun moving your data around! Will include overview replication for PostgreSQL in general, a tour of features, and a basic configuration walk through.

http://bucardo.org/wiki/Bucardo