AppRecs - AppRecs sorts through reviews in the App Store and automatically helps you filter out inauthentic results.
AppShopper - Mac Apps, Mac App Store, iPad, iPhone and iPod touch app store listings, news, and price drops
Zestia - Zestia is a mobile app designed to assist you in organizing your hectic schedule, social life, and professional persona.
AppAgg - Application Aggregator
Cydia - An alternative app store for jailbroken devices.
AlternativeTo - AlternativeTo lets you find apps and software for Windows, Mac, Linux, iPhone, iPad, Android, Android Tablets, Web Apps, Online, Windows Tablets and more by recommending alternatives to apps you already know.