A project that I always get my students to try is drawing an upside-down picture - something they can't recognize so they can only try to reproduce what they see with no preconceptions.
Something else I use with my students is Alphabet Art. I developed this when students were having trouble with basic shapes - the old 'I can't draw a circle' excuse.
Today I picked up the painted papers I did at a workshop with local artist Win Dinn (see last entry for contact info). These papers will be used in some of my mixed media art but I plan to keep some until next spring when I take 'Painted Paper 102'.