GitSpo - Measure & engage your open-source community
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.
Devo - Devo delivers real-time operational & business value from analytics on streaming and historical data to operations.
Ruby Toolbox - Explore and compare open source Ruby libraries
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.
moreofit.com - Moreofit is the first (and best) website similarity search engine.