Google has come up with their own answer to Wikipedia, with the introduction of Google Knol.
Instead of the Wikis Wikipedia relies on, Google's version relies on Knols or "knowledge units."
Just like Wikipedia, Knol users will be able to add their own content, edit other entries and will be able to rate existing articles. What Google is doing to set themselves apart is offering AdSense revenue on submissions, making it possible for frequent and popular contributors to earn money.
The articles will be displayed among the results in regular Google searches along with user rankings.
It's still going through its testing phase, but once launched, will be a huge threat to Wikipedia.