Create Your Own Buttons for the Google Toolbar
The Google Toolbar API lets webmasters create custom buttons for the Google Toolbar (version 4 and above) using XML. Buttons can navigate to and search a site, display an RSS feed in a menu, and change their icon dynamically. Users can add your custom buttons to their Toolbar by clicking on a link on your website or Google’s Button Gallery. They also aoffer a great Help section and host a Google Group for developers of the buttons and for anyone needing any answers related to it. In my opinon it is one of the best button makers on the net.