This website is a nice exemple on how web 2.0 turns websites into nice web application. Trullia is a real estate search engine that helps users find homes for sale and provides real estate information at the local level. Here are some nice functionnalities.
Google Map - All locations are located on a Google map so that users can view where the home is (with the map or satellite view)
FAQ - FAQ’s are written and answererd by users themselves. If you want to buy a house in a city, you can ask to the neighborhood if the location is nice, not too noisy…
Prices - You can view the Heat map that shows up how the prices have changed over the latest year.
RSS Feeds - You can subscribe to RSS feeds with your prefered locations.
Blog - And finally, they have a blog.