Grab the latest build of MySQL5 for OS X. Install everything (or at least the main package). The preferences pane is currently now working in Leopard, an update is expected soon, however for now you can open terminal and type:
sudo /usr/local/mysql/bin/safe_mysqld
once that’s running, open another terminal window (Command + n) and type:
sudo mkdir /var/mysql/
to create the directory and type:
sudo ln -s /tmp/mysql.sock /var/mysql/mysql.sock
to create a sym link to the default sock file. That should get you up and running.