A how-to on using WordPress to create microsites:

Landing sites are well known from the eCommerce world – ever experience you searched google for »cheap colgate toothpaste« and found an online reseller, and the site you landed on from google was exactly about colgate toothpaste? What if we grabbed the google search string from the visitor, and made the front page listing a mix of related posts to what he searched for and the newest posts?

Read more at WordPress: Creating landing sites