Inquisitor is a livesearch plugin for OS X’s Safari web browser. It gives the top few hits, spelling suggestions where appropriate, and links to jump to other search engines.
Garrett Murray’s ManiacalRage is an interesting blog on its own, but he’s also doing some good AJAX on his search interfaces. Look first at the archive search. But also take some time to appreciate the new content search. Sure, you’ll have some complaints, but it’s his site and not yours and there are some ideas there that are pretty interesting and useful.