ASO Tools by AppFollow - Tools for App Store Optimization in App Store & Google Play
Startup Toolkit - Interactive how-to guides to launch your startup
App Launch Checklist - Planning tool for launching your app successfully
Techstars Entrepreneur's Toolkit - Online resource to help you learn about entrepreneurship
StorePreviewer - See how your app will look like on the App Store
AwesomeHunt - Community-curated lists of learning resources on any topic.