If you're not using tags or taxonomy on your content, I urge you to start. Not only does it make it easier for people users to find things on your site (see the MFP 'Index'), it allows Google's robots to classify information from your site. I find a get a decent amount of traffic from 'long tail' searches.
Every so often, I study the terms people are using to find the site, and incorporate them into tags on the stories.