Here's an excellent website to help students understand the concepts of division.

 http://www.arcytech.org/java/b10blocks/b10blocks.html

Some reinforcement for decimals:

http://www.aaamath.com/B/dec.htm

http://www.mcwdn.org/Decimals/DecimalsMain.html

http://www.harcourtschool.com/activity/con_math/g05c03.html

Practice for finding area and perimeter of polygons:

http://www.funbrain.com/funbrain/poly/index.html

Tangram Website:

http://pbskids.org/sagwa/games/tangrams/index.html