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.
HypeStat - HypeStat is free statistics and analytics service, where you can find information about every website.
SimilarSites - Easily find more sites like those you like.
Site Rank Data - View historical rank information of websites via time series charts.
Product Hunt - A website that lets users share and discover new products
Q-Stats - Get free marketing insights for every question on Quora.