SimilarSites - Easily find more sites like those you like.

aiim - AIIM is the community that provides education, research, and best practices on information...

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.

JSter - JSter is a community-driven catalog of the most useful javascript libraries.

SimilarStores - SimilarStores is a free tool that helps you to find similar stores to any store!

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