merlyn responded with a typical PostgreSQL-advocate's response: PostgreSQL is the only "real" open source database. Databases are another area where TMTOWTDI applies. I heartily disagree with merlyn's advice that there's just no reason to recommend anything but PostgreSQL in a new installation.
The PostgreSQL vs. MySQL debate came up last week at the egovos conference. It's trivial to find people making presentations about and around MySQL at a conference today. Over the last year, it has been rather easy to find people making presentations about projects that were built around PostgreSQL, or couldn't have been completed without PostgreSQL (e.g. using PostGIS). In many ways, the debate is just tiresome; MySQL and PostgreSQL are interchangeable solutions for a wide variety of problems today. And if you need advanced features like triggers or stored procs, you can get them today with PostgreSQL or tomorrow with MySQL. Yes, ACID compliance is important, but MySQL's long success proves that it's not everything.
FUDding the issue doesn't help anyone. Neither does sneering at databases that don't fully implement Oracle's current feature list. Databases aren't rocket science, and sometimes all you really need is the standard basic feature set: tables, indexes, SELECT statements and maybe ACID compliance.