LiveReload - LiveReload 2 proudly presents… The Web Developer Wonderland. (a happy land where browsers don't need a Refresh button). CSS edits and image changes apply live. CoffeeScript, SASS, LESS and others just work.
Deku - Functional view library for building UI components as an alternative to React
Browsersync - Browsersync makes your tweaking and testing faster by synchronising file changes and interactions...
Preact.js - Preact is a fast 3kB alternative to React with the same modern API. Components & Virtual DOM.
CodeKit - CodeKit allows you to optimize the performance of your website by automatically and efficiently compiling a variety of popular languages.
w2ui - W2UI is a small JavaScript UI library with a complete set of widgets: layout, grid, sidebar, toolbar, tabs, fields, popup, utilities.