A how-to is an informal, often short, description of how to accomplish some specific task. They are generally meant to help non-experts, and may leave out details that are only important to experts, and may be greatly simplified from an overall discussion of the topic. See procedural knowledge for a discussion of what sort of knowledge is imparted, and how far it can be imparted, in how-tos.
Other types of instructional documentation include FAQs, manuals and guides. Wikipedia contains some procedural knowledge, partially listed below. For a list of how-tos related to Wikipedia itself, see Wikipedia:Help. Many additional how-tos can be found at Wikibooks:Main_Page.
http://www.eHow.com has a wide variety of how-to information. You can learn everything from how to throw a curveballto (http://www.ehow.com/how_1831_throw-curveball.html)how to tie a tie (http://www.ehow.com/how_2970_tie-tie.html) to how to buy a condominium (http://www.ehow.com/how_111174_buy-condominium.html)
For more about how to do something see the Know-How_Wiki (http://www2.iro.umontreal.ca/~paquetse/cgi-bin/wiki.cgi?Know-How_Wiki)(down, jan. 2005, will come back)
For more about how to perform a specific task in linux, see Linux HOWTOs (LDP) (http://www.tldp.org/)
For more about how to perform a specific task in Pick-style, see MultiValue HOWTOs (http://www.pickwiki.com/cgi-bin/wiki.pl)