Since I started doing the occasional consulting job for Open Query, I've seen a lot of MySQL servers that have been installed once and then forgotten about. This gave me the idea to do a short presentation about some basic MySQL server configuration. The first go was at DrupalCampMelbourne and I recently tried (and failed) to cram it into a three minute lightning talk slot at the LUV September meeting.
The title of the talk is (now) MySQL > YourSQL. I chose this not because I think that MySQL is better than the $other_database you use or because I may or may not run a newer version of MySQL on better hardware, but because I use InnoDB and not MyISAM as the default table format. More importantly, I do not run the server with the shipped default configuration.
Most distributions ship MySQL with a configuration file that sees you running a server optimised for a system with 32MB of RAM. That was great in 1996, but these days your Nike+ shoes have more capacity than that, so it makes sense to optimise the configuration - or at least to make it not suck quite as badly.
I chose InnoDB as the default storage engine not because it gives me a magic increase in performance or transaction support, but due to the improved reliability that comes from its ability to automatically recover from crashes better than MyISAM does.
All the following settings go in the [mysqld] section of your my.cnf file.