Apple introduced Dashboard and Widgets in 10.4 Tiger in 2005, and it's still alive and well. Jack of All Widgets is a universal search tool built for Dashboard, with dozens of built-in searches on many commonly searched websites, such as Amazon, Whitepages.com and Lyrictracker. It's pretty dated, but it actually still works, for the most part, though many of the links probably don't work anymore. The nice thing about JoaW is that it's easily customizable, all you have to do is edit an xml file in the widget package. While the widget itself has only one search field, the searches can be configured to accept text in any number of fields, by separating entries with a slash ("/"). It can be modified to work with GET or POST-type forms. If you still use Dashboard, check it out!
Download the latest version: Jack of all Widgets v2.3.6
Check out all the websites it searches, on Apple's download page click here.
The original User's Guide