Antone over at SEO SEO Secrets of the PageRank Masters has finally updated his blog with a post on determining what Google displays under your page title in search results which a few people have asked me about recently. I hope it helps.
‘So how do you control what text appears in Google’s search results? Make sure the search terms you are optimizing for appear close together early in your meta description tag or close together early in your page. If your site navigation appears above your content, put it at the end of the document, and use CSS to position in higher in the page instead of putting it at the beginning of the document. Then, hope that people use the search terms you’re optimizing for!’