Another tool which automates the process of keeping on top of keyword trends is Wordtracker. It's a paid subscription service, but offers a free trial.

It's no use peppering your site with keywords, if no one is looking for them in the search engines!

On a related note, here are four search engine pages that provide glimpses into search behavior and patterns: Google Zeitgeist , Lycos 50, Jeeves IQ and Yahoo! Buzz Index.