WikiProject: Here’s the interesting concept of the Wikiproject over at Wikipedia.
A WikiProject is a collection of pages devoted to the management of a specific family of information within Wikipedia. It is not a place to write encyclopedia articles, but a resource to help coordinate and organize article writing.
They seem like guidelines for how to handle a certain topic — what terminology to use, what information to be included, etc. It seems to be an attempt to get some consistency in an inherently inconistent system.
Wikiprojects may or may not have Wikiportals:
Wikiportals are Wikipedia pages intended to be the main pages for Wikipedians interested in a specific area of knowledge, helping both to find the information on the specific topic and to develop articles connected with it.
Surprisingly, there’s only about 20 of these. They’re very cool: like the Wikipedia home page, but just for a single topic. Check out the one on cryptography.