This poster about the element of line gives brief yet helpful information about different types of lines and how they can be used. I can see this kind of poster in any art classroom, along with more posters that deal with the other elements and the principles of art.
line art group project -- I would like to do this with computer graphics. Maybe with instructions that each student make a slide on powerpoint where something must start/end at certain grid points on the sides of the paper (a road, a ball, a line...). Then we print them all out and piece together on the wall.