One of the coolest features in Firebird is the integrated search bar in the menu. Its a small type-in that defaults to Google and returns the search query in the current tab. What makes it so amazing however is that additional search engines can be defined. Click on the default icon (A stylized G for Google) and you'll see a drop down with the option, "add engines..." - clicking this will take you to the Mycroft project on MozDev, where you can instantly install any of hundreds of additional search plugins.
I've currently got Amazon (.com, though the intl versions are also available), Bartleby world history, Dictionary.com, and Google News on there. Actually, I think I'm going to add Ebay right now... ok done. I actually just added Yahoo, IMDB, and Ebay - it just took me a few seconds.