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.
Free Software Directory - The Free Software Directory is a project of the Free Software Foundation (FSF) and United Nations...
SimilarSites - Easily find more sites like those you like.
JSter - JSter is a community-driven catalog of the most useful javascript libraries.
Product Hunt - A website that lets users share and discover new products
moreofit.com - Moreofit is the first (and best) website similarity search engine.