AppRecs - AppRecs sorts through reviews in the App Store and automatically helps you filter out inauthentic results.
Aptoide - Aptoide is a third party replacement for the traditional Google Play Store.
Cydia - An alternative app store for jailbroken devices.
Ninite - Ninite is the easiest way to install software.
Fnd - Browse Apple App Store and iTunes on the Web
Amazon Appstore - The Amazon Appstore is a place to purchase and download apps for your Android device.