Waffle Software has released a gem for us. Nuevos is a Mac OS X search utility allowing you to search using almost any web-based internet search engine, including ones you define, from a small window. This app is based on Huevos from Ranchero.com, but adds some great functionality.
I especially like this app because there is an optional menu item you can activate. I call it up with a keyboard shortcut and can instantly search places like Amazon.com, MacOSXHints.com, Technorati.com, Wikipedia.org and a ton of others. I’ve also imported some custom sites to search as well.
When you pull the search window up, you can use a keyboard shortcut to decide which site to search and off you go in your default browser.