MySQL, it's free and open source just like php

when you think of PHP you think of MySQL
when you think of ASP you think of Access

the most common type of webservers out there are:
LAMP = linux, apache, mysql, php

PHP has some built in mysql support along with another database or two that I cant remember off hand. You'll find alot of suppport for a php/mysql combo so thats the best route in my own opinion.

for php, i think mysql is best. its very easy to learn and capable of doing many things. plus theres lots of articles and tutorials with the php/mysql combination.

but if you're on a windows platform, you might want to look into PostgreSQL for php.

If you are thinking enterprise level, I would consider Oracle. For anything otherwise, MySQL would probably suffice. Especially, considering (MySQL) 4.1 and the upcoming changes in 5.

Some people use Postgres as well and it's meant to be as good as MySQL.

If your site is hosted you may notice that hosts talk about providing LAMP

thats
Linux <-- the server operating system, the opposite of windows
Apache <-- drives the websites
Mysql <-- the database of choice
Php <-- the website language

that's how well they all fit together. On top of that if you visit sites like Sourceforge or OpenSourceCMS you'll find that the best free software is written for LAMP.

Mostly, though, just talk to your host about what they offer and go with that. You'll find it's MySql 95% of the time.

Sarah

i would say both PostgreSQL or MySQL are great options i personally use MySQL for everything i do on my own. but at work we use PostgreSQL and they are both great systems and both free