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
Malavida - Alternative app store to Google play store
APKMirror - Android Market and APK Downloads
Apkecho - Apkecho.com makes it easy and fast for you to download Android games and apps for free
Aurora Droid - An alternative to the default F-Droid app with an intuitive UI and multiple features.
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.