Linux has an excellent <a href="
http://www.linuxvirtualserver.org/">Virtual Server</a> patch (built into more recent kernels I believe) which is great for load balancing. There are also a number of replication solutions for PostgreSQL.
I remember seeing a project which provided a really simple replicator for PostgreSQL, but can't find the link now. It was basically a proxy which emulates the PostgreSQL backend and sends off the requests to 2 separate PostgreSQL instances.
