While I absolutly love your site, I'm finding it harder and harder to get the chance to sit down and properly set up for some of the larger exercises. I was wondering if it could be possible to make a short list of exercises (preferably something that is more visually based) that can be done anywhere, from sitting on a bus, to breaks at work or school, or to have daily, weekly or monthly challenges designed to help various drawing skills at various levels?

Until there are more thorough lessons created as you suggested you can do quick sketches on your own. Quick sketches using real objects and scenes teach us how to see more accurately. You simply look for the most basic shapes when drawing an object or scene. For example a house is basically a cube with a triangle roof. Also look for the shadows in shapes and texture of objects and draw these as quickly as possible. You will be amazed at your results.

Bobby