Tangrams and pentominoes are easy to make, and you can buy very inexpensive plastic sets. You'll find tons of shadows and worksheets online that you can print and laminate, so it's easy to add more and more puzzles throughout the year.

for tangram patterns:
https://sites.google.com/site/polandbulldogmath/home/printables

for pentominoes:
http://www.scholastic.com/titles/chasingvermeer/pentominoes.pdf

I buy plastic manipulatives from Didex http://www.didax.com/, but you can find them at other online retailers and at most teacher supply stores if you have one near you.