Create a production WIKI with PHP

http://www.ibm.com/developerworks/edu/os-dw-os-php-wiki1.html

ASP.net Starter Kits - Ecommerce, Digg, Wiki, Portal and much more.

Explore and have fun.
http://www.asp.net/community/projects/

Also contains project based on ASP.NET MVC called Kigg which is a clone of Digg.
You can find it at http://www.asp.net/downloads/starter-kits/Kigg/