BetaList - BetaList provides an overview of upcoming internet startups. Discover and get early access to the future.
PitchWall - Browse new startups, and submit your mobile app/games startup's beta page here.
Product Hunt - A website that lets users share and discover new products
Betatesters.io - The platform connecting mobile developers and beta testers
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.
Beta Family - 50,000 testers to test your app