Apple has many tutorials on its website to help you learn more about the operating system and specific apps like iMovie and iPhoto. Often I have kids watch these after I give a brief introduction. I figure the folks in Cupertino, California who built the thing can probably explain it a little better than I can. For iPad help I direct you to the huge set of resources at iPadacademy.com.
Find out how - Great tips for PC users migrating to a MAC. (Welcome to the good side of life.)
Switch 101: The PC user's guide for learning about your Mac
Mac Higher Learning: The Next Steps
iLife tutorials (including GarageBand, iDVD, iMovie HD, iPhoto, iTunes, iWeb)
iWork tutorials (including Pages, Numbers, and Keynote)
More on iMovie
All things iPad from iPadAcademy.com (not Apple associated but full of great stuff).