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.
Passerine - Refined Product Hunt Desktop Client 🚀
Ruby Toolbox - Explore and compare open source Ruby libraries
aiim - AIIM is the community that provides education, research, and best practices on information...
LibHunt - LibHunt tracks mentions of software libraries on relevant social networks. Based on that data, you can find the most popular projects and their alternatives.
GitSpo - Measure & engage your open-source community