"Firefoxit is a Firefox extension that puts tiny little widgets or web applications on a kind of desktop launched from Firefox. Firefoxit has been tested on Windows XP, 2000, 98, Linux and Mac OSx86."
"Sometimes apps just don't look cool occupying an entire webpage. Firefoxit widgets are intended to be anything from a weather widget to a notepad or a spreadsheet."
The site: http://firefoxit.mozdev.org/
