Denver-based Sukle Advertising + Design created a great advertising campaign for water conservation in Denver. They illustrate the tagline “Use Only What You Need.” very cleverly by using only a portion of the advertising space. A great example is the billboard which has been exposed except for the area that contains the actual message.

Check out some of the outdoor shots:
http://www.frederiksamuel.com/blog/2006/11/denver-water.html

Plus, the accompanying videos are well done:
http://www.youtube.com/watch?v=0BT-QbqTZNY
http://www.youtube.com/watch?v=ebhBDmOwrfw

Dave Bobak