2nd Grade:
For the Teacher:
Place Value Movie
http://www.linkslearning.org/Kids/1_Math/2_Illustrated_Lessons/3_Place_Value/index.html

Building Numbers using Place Value Blocks
http://nlvm.usu.edu/en/nav/frames_asid_152_g_3_t_1.html

For the Students
Number Lines
http://www.harcourtschool.com/activity/mmath/2_nmln.dcr

Build a Train
http://media.emgames.com/emgames/demosite/playdemo.html?activity=M1A041&activitytype=dcr.

Test the Toad
http://www.bbc.co.uk/schools/numbertime/games/toad4.dcr

3rd Grade
For the Teacher
Building and Comparing Fractions
http://nlvm.usu.edu/en/nav/category_g_2_t_1.html

For the Student

Pizza Party
http://www.primarygames.com/fractions/start.htm

Fishy Fractions
http://www.iknowthat.com/com/L3?Area=FractionGame

Fraction Junction
http://www.linkslearning.org/Teachers/1_Math/6_Learning_Resources/2_SuperMath/content/games/fraction.htm

Fraction Frenzy
http://www.learningplanet.com/sam/ff/index.asp

4th Grade

Measurement, Shapes, and Transformations
http://www.bbc.co.uk/schools/ks2bitesize/maths/shape_space_measures.shtml.