You might also find that you want something really stripped down. Two options to consider are [link|http://www.sleepycat.com|Berkeley DB] (not relational) and [link|http://www.hwaci.com/sw/sqlite/|SQLite] (relational but very minimal).
Cheers, Ben
"good ideas and bad code build communities, the other three combinations do not" - [link|http://archives.real-time.com/pipermail/cocoon-devel/2000-October/003023.html|Stefano Mazzocchi]