I have the old tried and true "How to draw" book pile. I also have a pile of
"Anti-coloring book" type worksheets ready. Cleaning for extra credit works
with some kids (some of the extra-squirrelly students are wizz-bang
cleaners/organizers). Also I'm lucky enough to have 4 computers in my classroom, so I use
the interactive Sanford Artedventure site or Painter 6 or Goo. The trick is to
have something that is absorbing but not more interesting than the project
you are doing, so they won't rush through to get to the extra stuff.