How to setup a PostgreSQL cluster Could you point me to a good book about setting up a PostgreSQL cluster? The goal is to set up an active-passive cluster spread across two different data centers to achieve high availability.
There are a few problems with any recommendations here.  The basic issue is that you have a set of tradeoffs in all replication solutions that you won't find in a single source. 

The simple approach is to start with the documentation and work on setting up the built-in replication.  The manual is a good place to start there.  If all you want is a copy of everything that's what you want.  Pay close attention to the hardware and software points there and make sure the systems are essentially the same architecture and OS (i.e. both 64-bit, and both Linux).  Ideally they should be the same OS version and PostgreSQL compiled with the same options (binary packages are good here).

However if that doesn't cut it, here are some book recommendations:

"PostgreSQL 9.0 High Performance" by Greg Smith
and
"The PostgreSQL 9 Admin Cookbook" by Simon Riggs and Hannu Krosing.