Momentum is building around documentation best-practices at Eclipse. EGit, Eclipse's Git integration project, recently became the latest project to adopt a crowdsourcing approach to documentation, and is reaping the benefits: in one day they've already seen the contribution of Git for Eclipse Users from Alex Blewitt.
They are able to do this by taking advantage a new feature of the latest Mylyn WikiText, which can generate Eclipse help directly from a wiki. While it was possible to process individual pages before, now Mylyn WikiText makes it easy to process multiple wiki pages at once while automatically downloading images, maintaining page cross-references, and building a unified table of contents.
You can learn more about crowdsourcing documentation at EclipseCon 2010, where Chris Aniszczyk and I are co-presenting Documentation: Single-Sourcing, Crowd-Sourcing And Other Voodoo. If you can't wait two weeks, you can find out how they're doing it at EGit from their contributor guide.
Updated 4/21/2010: Thanks to Chris, a working example with documentation and source is available at DocumentationGuidelines/CrowdSourcingExample