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
Free Software Directory - The Free Software Directory is a project of the Free Software Foundation (FSF) and United Nations...
Similar Site Search - SimilarSiteSearch helps you find similar, related, or alternative websites.
Filehippo - Filehippo is your key to opening files that Windows claims are "in use by another user" or simply "can't be found." Avoid the hassle.