http://illuminations.nctm.org/
Math will come alive in your classroom using the interactive resources available at Illuminations. There are more than 600 lessons searchable by grade level, topic, and standard. There are more than 100 interactive online activities such as data graphers, dynamic paper (create 3-D images), a fractal tool, a tessellation creator, and algebra tiles that you can use with a smartboard to illustrate complex math concepts in the classroom. Illuminations was created by the National Council for Teachers of Mathematics.