There is a really snazzy java based data modeling tool available over at http://www.sqlpower.ca/page/architect . If you drill down on the “Try” button and look way down at the bottom, almost hidden, you will find a link to the free “Community Edition”.
Just for fun I pulled up an old copy of a WordPress Mysql database. Its not the current version, in fact I’ve lost track of what version it was. In any case I reverse engineered the model very quickly with Power Architect. This looks like I also forward engineered it to a DB2 platform because the text fields are now CLOBs.
Here is the model I produced. I made all relations non identifying, and completely ignored cardinality etc. Its far from a finished product.