Fredrik Lundh put the Python tutorial in a Wiki. One week later it he's seen 175 edits. It's probably the most important Python documentation project going. There haven't been 175 edits to the tutorial in the last five years.
For years, I maintained that Python's documentation tools were just fine. People suggested all sorts of new tools and gimmicks, and I thought that they didn't improve on what we already had. Sure, Latex is hard to format and the tools are a little cumbersome, but writing documentation is hard, so surely the tools aren't the issue. (See stop energy and space-program architecture discussions.)
I'm happy to see I was completely wrong. Removing barriers to entry is critical for this kind of collaboration. Every barrier turns away a few people until you're left with a few people who are committed but too busy to do anything. The Alternative Python Reference has exactly the right goals