I present you with the CSS Stress Test bookmarklet.
Create your own "requires-jQuery-to-run" bookmarklet!
dotEPUB is a browser bookmarklet (or favlet) that tries to get clean text content and metadata from webpages to ease the automatic e-books conversion.
YAML Debug is ... ... an assistive tool for web developers, that allows you to quickly review code quality and semantic structure of any website (particularly those based on YAML) as well as testing it against common oversights. This tool is not intended to be a reliable test environment for the accessibility of websites!
With this bookmarklet you can click a html element and get and edit an XPath/CSS Path expression to it.
Lazy Sheep is a del.icio.us bookmarklet that auto-tags and auto-describes your bookmarks.