Please use the following list of links for more information:
Francois Marier has written a short-and-to-the-point article on tracking down sudden PostgreSQL performance problems, which is definitely worth reading.
Gregory Smith: PostgreSQL 9.0 High Performance
boxinfo is a Perl script for quickly gathering all sorts of interesting information about a particular computer, which is then put into a HTML or MediaWiki page. It is very handy for being able to see a quick overview of the boxes that you are responsible for. The script has a highly developed Postgres section. It was developed at End Point Corporation by Greg Sabino Mullane.
Profiling with perf: The Linux kernel comes with a performance analysis tool called perf that can even be used on production servers to analyze the call stack of a server, or a process. This is useful to find the bottlenecks of a query processing or simply of a server running and improve those.