AppShopper - Mac Apps, Mac App Store, iPad, iPhone and iPod touch app store listings, news, and price drops
UserGuiding - User onboarding made easy, for less. Create product walkthroughs in a couple of clicks, without breaking the bank.
AppAgg - Application Aggregator
Usetiful - Fight user churn with great user onboarding. Interactive product tours and smart tips significantly improve your user retention.
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.
Userlane - Digital adoption platform with interactive guidance for software applications allowing anyone to understand and master any software from the get-go.