A few days ago I posted about the Porter Square snowdecahedron. Here are more pictures of it and pictures of some smaller ones. The project is due to Dan Beyer. He previously made a dodecahedron out of a tree stump (apparently the trick is to make a wedge corresponding to the dihedral angle of the dodecahedron beforehand) and has proposed dodecahedra built of traffic cones as public art for construction sites.
(I found Dan Beyer's site via metafilter; I don't recall how I found the original picture on flickr linked to in the previous post.)