Induction: A Polyglot Database Client For Mac OS X 
Serious question:Can't someone just add database drivers to Sequel Pro? It's far and away the best Database GUI I've ever used and its reliance on MySQL is actually keeping me from moving to PostgreSQL full time.(i.e. http://www.sequelpro.com/ and http://www.sequelpro.com/docs/Source_Code - a little crazy they're still on SVN but oh well)