UX Challenges - Done reading about UX? Start doing it.
ASO Tools by AppFollow - Tools for App Store Optimization in App Store & Google Play
Uxcel - The easiest way to learn UX/UI design
App Launch Checklist - Planning tool for launching your app successfully
uxtoast: Learn UX Design - Become familiar with design laws and learn how to use them.
StorePreviewer - See how your app will look like on the App Store