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.

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.

Ruby Toolbox - Explore and compare open source Ruby libraries

Product Hunt - A website that lets users share and discover new products

GitNews Web - Trending repositories from GitHub, HackerNews & Reddit

Free Software Directory - The Free Software Directory is a project of the Free Software Foundation (FSF) and United Nations...