DOM Monster Bookmarklet : DOM Monster is a cross-platform, cross-browser bookmarklet that will analyze the DOM & other features of the page you're on, and give you its bill of ...
Huginn : Huginn is a system for building agents that perform automated tasks for you online. They can read the web, watch for events, and take actions on your ...
manifestR is a bookmarklet, which you drag to your bookmarks bar. Then, when you visit any page, you can click the manifestR button, and it will create an HTML5 appcache manifest file for that page.