Here are some great examples of unique playgrounds that offer an innovative approach to play and learning:
http://www.ptotoday.com/pto-today-articles/article/363-a-playground-that-teaches-science
http://www.sugarsandpark.org/playground.htm
http://cgpartnersllc.com/exhibits/hallofscience.html
I would also recommend EVOS from Landscape Structures:
http://www.playlsi.com/Products/Playsystems/Evos/
EVOS takes traditional playground elements (slides, monkey bars, ropes, etc) and puts a wild, "space-age" looking twist on the playground. We are building the first EVOS playground in the metro Atlanta area on April 10th at Victory Park in Marietta. The kids can't wait!
You can see some great pictures of the Evos equipment and kids playing on it here.
Also, you should check out information on the new partnership between KaBOOM! and Imagination Playground - a whole new kind of playground built around creative play!