Nokia Support has published a series of Nokia Lumia 800 and 900 tutorial videos over its official YouTube channel, some of which are embedded below for convenience. Good stuff, even if seasoned AAWP readers will already know most of the information being imparted, from setting up Office365 to viewing message conversations.
Nokia Lumia 900 – Get Started:
Set up Office 365:
Share your mobile data connection:
Tips and Tricks (demoed on the smaller Lumia 800):
Viewing conversations (also demoed on the Lumia 800):