The article, entitled "Switch 101: On Windows I used to..." is part of Apple's Switch 101 series which is directly aimed at getting recent switchers comfortable with using OS X. It covers such tasks as finding and opening files, quitting applications, and using shortcut key modifiers (such as , the Command key).
I have shown this article to many recent switchers both in my family and otherwise; it has always proved to be a valuable resource to those that are new the Mac platform. Another great resource for recent switchers is TUAW's own Mac 101 series. Do you have any other tips for recent switchers? Post them in the comments and share the wealth of your experiential knowledge.