After installing the newest mySQL package, then trying to startup mySQL from my preference pane, it would simply not start. I did a quick search on Google and instantly found an article which helped. The advice given by the blog author did not work, but after reading through some comments I found the answer:

(Macbook Pro, Leopard, MySQL 5.1.23 pkg )

Start - sudo /usr/local/mysql/support-files/mysql.server start
Stop - sudo /usr/local/mysql/support-files/mysql.server stop

Important that you run that as root (sudo) otherwise mysql.sock doesn’t appear in /tmp/