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.
SimilarSites - Easily find more sites like those you like.
Product Hunt - A website that lets users share and discover new products
Slant.co - Slant is a collaboratively edited resource that helps you quickly make decisions.
Sites Like - Siteslike opened it's doors to the public on the 4th of december in 2008, since that time...
SimilarStores - SimilarStores is a free tool that helps you to find similar stores to any store!