The new MySQL Workbench is now in beta and is looking very good:
You can import create scripts (mysqldumps), build diagrams yourself, with full drag and drop etc, and export create scripts. You can also annotate with text and images and export the diagrams as SVG, PDF, PNG etc… Here’s the PDF for the MODx 0.9.6.3 diagram shown, along with the MWB (workbench) file. That diagram is just an imported mysqldump of a MODx DB – all I did was click the auto-arrange button.
It’s available for Linux (32 & 64 bit), Mac and Windows. I’ve been playing with the 64bit version in Ubuntu and it seems to work great! More info on their blog, or get it here: http://dev.mysql.com/downloads/workbench/5.1.html
Posted a link to the MySQL Workbench forums: http://forums.mysql.com/read.php?153
As another example, see Wikipedia’s Data Model: http://www.mediawiki.org/wiki/Manual:Database_layout
http://www.mediawiki.org/wiki/File:Mediawiki-database-schema.png
OpenMRS (Medical Record System) Data Model:
http://openmrs.org/wiki/OpenMRS_Data_Model_Documentation
http://openmrs.org/images/5/59/Openmrs_data_model_1.10.png