vsChart.com - With vsChart.com you can compare products and a lot more.
Versus - Find popular alternatives to anything in a jiffy
Diffzi - Diffzi.com lets you compare anything.
Productz.com - Crowdsourced products database
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.
Kimovil - Compare price, specs, reviews and benchmarks for smartphones and tablets.