A client asked me to find a good example of a wiki that taught people how to use a specific application (Wikipedia is overwhelming to most, and due to the vastness, not a great example for smaller implementations). The best I found was this, for learning how to use Python. While most here may not be interested in Python, I think it is worth a look to see how content is structured.

Again, I personally find the imperfections satisfying, as it reflects a reality not a vision, and what the client could reasonably hope to achieve.