Marty Cooper, who goes by the name "Hombre McSteez," animates in plein air, using felt-tipped markers, whiteout, transparency cels, and an iPhone. He calls the result "Aug(de)mented Reality." Here's the latest.
Mythbuster co-creator Adam Savage invited Marty Cooper to his workshop for a behind-the-scenes video, in which they actually create one of the segments in one day. (Link to video)
Here's the original video, which has racked up more than four million views.
For a good introductory book on animation technique, check out: The Animator's Survival Kit: A Manual of Methods, Principles and Formulas for Classical, Computer, Games, Stop Motion and Internet Animators