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
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.
APKMirror - Android Market and APK Downloads
Mobango - Mobango is an alternative Android market.
Samsung Kies - Samsung Kies is a freeware software solution used to communicate between Mac or Window OS and more recently Samsung smartphones and tablets.
Amazon Appstore - The Amazon Appstore is a place to purchase and download apps for your Android device.