F-Droid - F-Droid is an interesting alternative for Android users who want to try something different and not have to use the Goole Play store all the time.
The Y Combinator Database - The definitive database of YC companies with all the metrics
APK Pure - Download apk for Android with APKPure APK downloader. NoAds, Faster apk downloads and apk file update speed. Best of all, it's free
Startup School - How to start a startup, by Y Combinator
APKMirror - Android Market and APK Downloads
Apply to YC (Y Combinator) - Curated collection of resources for founders applying to YC.