Wikis in Action — The Top 57 Wikis by Rank
This is a list of the top 57 wikis (by rank). It's interesting to see how they are being used and which wikis they're using. One thing Katriel Reichman said in the wiki interview the other day is that wikis are often best used when the topic is reference information. I haven't gone through each of the 57 wikis, but I bet one could learn a lot by perusing them for a few days.
I found this list by searching for wikis in del.icio.us, the most popular social bookmarking site.
About Tom Johnson

I'm a technical writer based in the Seattle area. In this blog, I write about topics related to technical writing and communication — such as software documentation, API documentation, visual communication, information architecture, writing techniques, plain language, tech comm careers, and more. Check out simplifying complexity and API documentation for some deep dives into these topics. If you're a technical writer and want to keep on top of the latest trends in the field, be sure to subscribe to email updates. You can also learn more about me or contact me.