I have to think a bit about how a Wiki really works. On one hand I don't like the idea of mixing advanced coding tips with rudimentary how to stuff if it dilutes the focus on code. But on the other hand, a Wiki is not organized in a way that one topic has to take away from another. I'm basing this on Wikipedia. I'm not sure all Wikis work the same way.
I think it is important to have a strong platform for the people dedicated to code modules and people that want to learn how to code them.
I kind of like how the manual on php.net works. On a page about a PHP command there will be an official explanation of the command and a few simple examples. Underneath users comment and contribute with their own code snippets. Example:
http://se2.php.net/manual/en/function.substr.php
Unfortunately I don't know what they are running it on (well something made in PHP obviously but...).
[Edit:] If I could add something to the way the php manual pages works it would be to have the comments threaded so that they were easier to follow.