Alternato - NOTE: Not available in English.
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.
AlternativePedia - Discover free, open source or simply better alternatives for your software based on our research...
SimilarSites - Easily find more sites like those you like.
Aventrix - Aventrix is a website that helps you discover new and fun activities.
Product Hunt - A website that lets users share and discover new products