Just discovered MySQLTuner, a very nifty little perl script that will (read-only) analyse your MySQL install and suggest different configuration changes to make it work better. Going to be using this a lot I think.
MySQLTuner is a script written in Perl that allows you to review a MySQL installation quickly and make adjustments to increase performance and stability. The current configuration variables and status data is retrieved and presented in a brief format along with some basic performance suggestions.