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
SimilarPages.com - SimilarPages has found and classified millions of interesting sites hidden due to low popularity with the goal of helping you discover and search a larger portion of the web
The Startup Pitch - A place for startups to share themselves with the world.
SimilarSites - Easily find more sites like those you like.
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.