Amazon Appstore - The Amazon Appstore is a place to purchase and download apps for your Android device.
AppAgg - Application Aggregator
GetJar - Discover and play paid apps and games for free.
AppRecs - AppRecs sorts through reviews in the App Store and automatically helps you filter out inauthentic results.
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.
Fnd - Browse Apple App Store and iTunes on the Web