Unspace has a great article on what they’re calling LiveSearch. There are few great examples of this display, then filter approach at work. One of my favorites sites is the Trulia.com site in the US that provides a Real Estate search. They’re continually improving the interface but the basis premise is get the user listings as quickly as possible and then let them filter to find what they want. When combined with an AJAX interface, it can be a really powerful user experience.