Growing Page - Browse web projects and evaluate them by multiple criteria.
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.
PitchWall - Browse new startups, and submit your mobile app/games startup's beta page here.
Ruby Toolbox - Explore and compare open source Ruby libraries
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
GitSpo - Measure & engage your open-source community