Canon's own Rudy Winston has posted some very helpful tutorials on how to maximize the AF systems found on the 5DIII and 1Dx. I found them much more helpful than the instruction manual, and wish I had read them before taking the 5DIII on my first shoot. There's a great explanation of cross-point AF sensors, too. The new AF system is probably an easy transition for 7D users, but for people stepping up from 5DC/II's and xxD's, there's much to learn. I'm not sure if these have been posted yet, but here goes:
Menu system
http://learn.usa.canon.com/resources/articles/2011/1dx_af_menu_article.shtml
Multiple AF points
http://learn.usa.canon.com/resources/articles/2012/5d3_multiple_af_points.shtml
AF Configuration tool
http://learn.usa.canon.com/resources/articles/2011/1dx_af_config_article.shtml
Cross-type sensors
http://learn.usa.canon.com/resources/articles/2011/1dx_af_precision_crosstype_article.shtml
AF points and area selection
http://learn.usa.canon.com/resources/articles/2011/1dx_af_pts_article.shtml
Menu system
http://learn.usa.canon.com/resources/articles/2011/1dx_af_menu_article.shtml
Multiple AF points
http://learn.usa.canon.com/resources/articles/2012/5d3_multiple_af_points.shtml
AF Configuration tool
http://learn.usa.canon.com/resources/articles/2011/1dx_af_config_article.shtml
Cross-type sensors
http://learn.usa.canon.com/resources/articles/2011/1dx_af_precision_crosstype_article.shtml
AF points and area selection
http://learn.usa.canon.com/resources/articles/2011/1dx_af_pts_article.shtml