Dan Benjamin at Hivelogic has some excellent guides for setting up all sorts of things on a Mac that relate to Rails development. His guide to installing MySQL on OSX is no exception. It takes you through the steps of downloading, compiling and installing the MySQL source code on your local machine. If you want MySQL on Leopard, this is probably the best way to go. There currently is no installer package for Leopard and while there is a package for Tiger, it is not without issues. Besides, it’s so much more fun to compile from source.