Bootstrap 4 Cheat Sheet - An interactive Bootstrap 4 cheat sheet
App Review Times - Find out the average app review times for iOS & Mac apps
Bootstrap Zero - Open-source, free Bootstrap templates collection.
App Reviews Dashboard by Appfigures - Monitor, analyze, and reply to app reviews in one place
HackerThemes - Bootstrap 4 themes and tools for web developers
PitchWall - Browse new startups, and submit your mobile app/games startup's beta page here.