The Maatkit article on Wikipedia was removed some time ago, after being deemed not notable. I believe this is no longer the case. It’s hard to find a credible book published on MySQL in the last few years that doesn’t mention Maatkit, there’s quite a bit of blogging about it from MySQL experts and prominent community members, and the toolkit is certainly in wide use — it’s important enough that notable companies are supporting its development. It’s available through every major Unix-like operating system’s package repository. On Debian, it’s actually part of the mysql-client package, so if you install MySQL, you automatically get Maatkit too. I believe it’s probably the second most important set of MySQL command-line tools; the most important, of course, is the set of client applications that is included with MySQL itself.
But my opinion on this topic is beside the point. I’m the creator, and I’m biased. The Maatkit Wikipedia article should be created by independent people, not the project’s founder. If you think that Maatkit belongs on Wikipedia, I encourage you to help write that article.