The new version of MSDN online has a great feature that allows users to add text to existing pages. In a way it turns MSDN into a giant wiki while drawing a firm line between user-submitted content and official Microsoft content.
The feature hasn't been out in the wild for long, so every page doesn't have user content, but I ran into a great example today. I'm writing a program that fires up a process and captures both stderr and stdout. The original MSDN explanation warns of possible deadlocks and says that you can use multiple threads to avoid the problem. User fatcat1111 added onto the article with a thorough example of using two threads to capture stderr and stdout. Fantastic!