A puzzle using geomety:
http://www.aplusmath.com/cgi-bin/Games/geopicture
Isometric drawing:
http://illuminations.nctm.org/ActivityDetail.aspx?id=125
Polygon playground:
http://www.mathcats.com/explore/polygons.html
Polygon game:
http://www.math-play.com/Polygon-Game.html