Keyword Box adds a toolbar item which invokes a script or URL with the text you enter. The script can be customized to your needs or you can use one of the sample scripts provided by the extension. Keyword Box includes the following sample scripts:
Web Dev Lookup
functions or PHP functions (useful for web
Highlight (and a yellow background) to each
occurrence of a word or phrase on the currently
loaded web page.
Go to Mozilla Bug
View Mozilla bug reports including those for
Firefox and Thunderbird.
Get weather information for U.S. locations
(useful for people who travel often.)
Show information from Google Maps.