Blizzard have done various videos to help those who are newly 90 (aimed, I believe, more at those who used the "free level 90" option with the WoD pre-order). They are very short and only cover certain specs for each class, at the moment, but possibly worth a look at all the same:
http://eu.battle.net/wow/en/blog/14005221/leap-into-action-with-our-new-level-90-crash-course-videos-19-05-2014
