Appsolite - Evaluating software is laborious, time consuming and riddled with a lot of guess-work.
LibHunt - LibHunt tracks mentions of software libraries on relevant social networks. Based on that data, you can find the most popular projects and their alternatives.
Social Media Tools Comparison - Compare 150+ social media management tools' plans
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.
Product Comparisons - Compare any 2 software products
JSter - JSter is a community-driven catalog of the most useful javascript libraries.