Hey. Please go here (Google search): http://www.google.com/search?hl=en&q=yahoo&btnG=Search See the first result. Its about Yahoo! Under that link is a small description: 1 Apr 2009 ... Welcome to Yahoo!, the world's most visited home page. Quickly find what you're searching for, get in touch with friends and stay ... How can I do that with my wordpress blog ? Thanks.
I'm not sure how Yahoo did this as they have no meta description and that text is not on their page. Either they are doing some kind of cloaking or this text was extracted from another source....google webmaster tools, cached data or a directory listing. You can do this quite simply by setting your homepage description meta tag.