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.
JoyDownload - Collection of free software and shareware programs to download
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
osalt - Find open source software alternatives to well-known commercial software.
APKMirror - Android Market and APK Downloads
IceWalkers - IceWalkers.com provides a vast database of Linux Software.