Several months ago I wrote an article on tuning your PostgreSQL database for performance that has gained a lot of attention. While I think the article covers most of the basic to intermediate level options you can use to better tune your database server, it is by no means all you're ever going to need to know. If you use PostgreSQL often I strongly suggest you at least scan the posts on the postgresql-performance mailing list.
What surprised me most is how many companies and individual developers that are in need of a consultant to help them get the most out of their PostgreSQL setup. Because of this we've launched a new PostgreSQL Performance Tuning Service designed to help organizations receive better performance out of their systems and reduce the need to upgrade their server hardware. We often find that a few well placed configuration, query, or stored procedure changes can dramatically impact the speed of your application or website.
The problem with online tuning guides and the standard documentation is that every company's database is designed and/or used just differently enough from everyone else that a customized tuning is the best option. Contact us to find out more and schedule a performance analysis.