Google operate a Web 2.0 search engine called SearchMash with an Ajax based interface.

Features of this search engine are:

URL menu
Click the green URL of a web result to open a menu of options for viewing the URL or refining your query like Open in this window, Open in a new window, open cached copy, more from this site and more similar pages

Image results panel
Shows the top three image results next to web results.

Reorder results
Click the number next to a result and drag it around to reorder. This is just for fun right now, but we have some ideas for how to use this.

More results bar
Click the “more results” bar at the bottom of the page (or hit the space bar) to load more results and automatically scroll down to view them which is definitely awesome

Link- www.searchmash.com