Wikipedia articles that explain how to do something:
- How to write a Java applet
- the Wikipedia Cookbook
- How to add content to Wikipedia with minimal effort
- How does one edit a page
- How to solve the Rubiks Cube
About 400 HOWTOs on Linux are published by the Linux Documentation Project. Many of them are licensed under the GNU Free Documentation License and can be included in the Wikipedia as long as attributed properly.
There is an excellent argument for including this sort of information in an encyclopedia: an encyclopedia is a compendium of human knowledge. Usually, encyclopedias describe little of what epistemologists call procedural knowledge, or knowledge of how to do things. Since this is a kind of human knowledge, and since it can, sometimes, be usefully imparted via prose (as well as, or instead of, by direct demonstration or teaching), an encyclopedia should include articles describing procedural knowledge.