I've come across a few articles on how to optimize WordPress performance (all of the following links come from the first linked story in the list below):
- Wordpress Performance: Why My Site Is So Much Faster Than Yours
- Optimize WP Loading Times
- Optimizing Wordpress Performance
- Optimizing Wordpress for High Volume Traffic
- High Performance Wordpress
- Diggproof & Speed up Your Wordpress Blog
WordPress is by far my favorite content management system, but I opted to use Movable Type over at Born Geek, mainly because it uses static HTML pages (which load faster). Considering the content in the above guides, I may eventually switch from Movable Type to WordPress.