I've completed a Postgres port of WordPress 1.2, which appears to be fully working on my machine. It includes a script to convert from an existing MySQL database for those of us out to purge the inferior RDBMS' from our boxes ;).
WordPress-Pg will have a SourceForge page once the project is approved. In the meantime, it's availiable at http://www.gotroot.ca/wordpress-pg/.
Any input, especially bug reports, is welcome. I can be reached via e-mail at email@example.com.