There had often been talks and some times flame wars when there had been comparison between MySQL and PostgreSQL. Each database has its own strength and weaknesses. As an initiative, I thought to do a little research on this topic and to list down the common points gathered in a tabular format.

Comparison MySQL PostgreSQL
License GPL/proprietary license. Those not wanting to abide to those terms may buy a proprietary license from MySQL Inc. BSD-like license
Redistribution Any redistribution of the binaries must be accompanied by the source code from which they are derived, whether original or modified Binaries and source code are available free of charge
SQL Standard compliance MySQL had many problems with SQL standard compliance. It was only from ver. 4 they started supporting transactions/foreign keys. Cases of data loss in In comparison, PostgreSQL complies to SQL standard and has extensive list of features to support
Speed MySQL''s main concentration was on speed when it was developed. Even then, it happens only if there is low level of concurrent users. When the load increases it has a drastic impact on MySQL Postgre adheres to ACID model and scales well when the number of concurrent users increase.
Support User base for MySQL is more and there are more web hosting companies offering MySQL in comparison. Hence there are more forums to solve your problems when in need. PostgreSQL has equivalent number of mailing list offering support and a list of commercial companies offering their services
Interface phpMyAdmin phpPgAdmin

The list will continue to grow …