Memex : Browser Extension to full-text search your browsing history & bookmarks.
Browser Calories : The easiest way to measure your performance budget.
When can I use... : Compatibility tables for support of HTML5, CSS3, SVG and more in desktop and mobile browsers.
Browsh : Browsh is a fully-modern text-based browser. It renders anything that a modern browser can; HTML5, CSS3, JS, video and even WebGL. Its main purpose is...
chromeless : The chromeless project is an experiment into making it possible to build a web browser using only web technologies, like HTML, JavaScript, and CSS.
Measure between the following elements: images, input-fields, buttons, videos, gifs, text, icons. You can measure everything you see in the browser.