iNoJB - iNoJB, formerly iNoCydia, is an amazing Cydia alternative requiring no jailbreak!
AppRecs - AppRecs sorts through reviews in the App Store and automatically helps you filter out inauthentic results.
Cydia - An alternative app store for jailbroken devices.
Fnd - Browse Apple App Store and iTunes on the Web
BuildStore - Safe and trustworthy alternative app store for iOS
Apple App Store - Install apps on your iDevice via the App Store.