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.
Toole - Search for and discover online tools
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.
Rage Grade by FullStory - Benchmark your customer frustration
JSter - JSter is a community-driven catalog of the most useful javascript libraries.
F*** You Pay Me (Beta) - Made by influencers, for influencers.