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.
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Productz.com - Crowdsourced products database
Alternative.me - Welcome to alternative.me, the source of better software alternatives. Finding suitable software was never easier.
Kimovil - Compare price, specs, reviews and benchmarks for smartphones and tablets.