Sticklet permits to customize the user experience while browsing. It enables the augmentation of the visualization of a web page in an easy and safe way. In other words, while you are browsing a concrete web page, this can be enhanced with information retrieved from other web page or web service.
Hundreds of scripts, for a wide variety of popular sites, are already available at http://userscripts.org.
The creation of such scripts is out of the normal user scope and its shareability is hindered because there are some security issues with the usage of Greasemonkey.
More information about the Sticklet’s theoretical base at http://dl.acm.org/citation.cfm?id=2460383.2460388
Some examples are available at http://userscripts.org/users/sticklet.
Pre-release version available at Sticklet.
Sticklet operates on top of Greasemonkey, so the installation of Greasemonkey is required in order to make Sticklet work. https://addons.mozilla.org/firefox/addon/greasemonkey/