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.
Skuuudle - Discover, match and monitor your eCommerce competitors.
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
Price2Spy - Price2Spy is a price monitoring, pricing analytics, and repricing tool, meant to help eCommerce professionals keep an eye on their competitors or retailers.
APKMirror - Android Market and APK Downloads
BuiltWith - Find out the technology behind websites