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.
Cydia - An alternative app store for jailbroken devices.
1Mobile Market - 1Mobile Market is one of the newest apps and games places where the exclusive download of games and apps is accessible.
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.