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.
Site Rank Data - View historical rank information of websites via time series charts.
SimilarSites - Easily find more sites like those you like.
SimilarWeb - SimilarWeb.com is a website analysis tool that gives you analytics information for any website.
Product Hunt - A website that lets users share and discover new products
Quantcast - Quantcast Corporation is a digital marketing company that provides free audience demographics measurement and delivers real-time advertising.