Replication: Mammoth Replicator
Command Prompt supplies the best replication available for PostgreSQL. They support it on RedHat and SuSE at the very least. So far, they have been willing to support Gentoo also. That is pretty hot.
I am working on getting it deployed. Along the way I'm producing some solid administration documents for my clients, and trying to make some nice wiki howto related to it.
I have not succeeded due to as-yet unknown bugs in something that I have done. However, I hope to soon have it up.