WikiUncle

Wiki Uncle is a collaborative wiki containing articles on comparisons between two (or more) products / stuffs/ things / terms / etc. Wiki Uncle is designed to house comparison articles, which makes this project unique and differentiates it from other wikis. Any person / organization can contribute comparison articles to Wiki Uncle. As Wiki Uncle has only recently started so has few articles. Examples of articles include comparisons between:
 * Apple iphone vs Samsung galaxy S2
 * Cyclone vs Tornado
 * Fusion vs Fission
 * Sun Java vs Microsoft.net
 * Cube vs Cuboid
 * Iphone3 vs Iphone4
 * Animal cell vs Plant cell
 * Alligator vs Crocodile
 * Java abstract class vs Java interface

The list is endless.... The wiki started in 2011 and uses MediaWiki.

Related wiki:
 * Debatepedia wiki also has side-by-side comparisons, but generally about more abstract concepts in morality, economics, etc.