SketchCasts - A weekly screencast, all about how to use Sketch
Startup Toolkit - Interactive how-to guides to launch your startup
Base UI Sketch Framework - Huge set of everything you need to design and prototype
Techstars Entrepreneur's Toolkit - Online resource to help you learn about entrepreneurship
Remake - A way to make web apps with just HTML & CSS
App Launch Checklist - Planning tool for launching your app successfully