Querious looks promising:
Querious is a new MySQL database management application written from the ground up exclusively for Mac OS X Leopard. Unlike mindless Mac OS X versions of applications made for Windows or Linux, Querious is a stunning new app that is precise and easy to understand, giving you full control without getting in your way.
I used to use CocoaMySQL but the project was abandoned and has since resurfaced as Sequel Pro. Apparently Querious is much faster at working with large data sets.