Area & Perimeter http://www.mathplayground.com/InteractiveGeometry.html
Interactive Activities http://www.cut-the-knot.org/Curriculum/index.shtml
NCTM Activities http://nlvm.usu.edu/en/nav/grade_g_3.html
Circumference Activity http://www.harcourtschool.com/activity/elab2002/grade_4/023.html
Prime Factors http://nlvm.usu.edu/en/nav/frames_asid_202_g_2_t_1.html
Exponents http://www.aaastudy.com/exp-eval-squ1.htm
Factor Game http://illuminations.nctm.org/ActivityDetail.aspx?ID=12
Decimals http://www.aaamath.com/B/dec37ax3.htm
Multiplying Decimals level 1 http://www.funbrain.com/cgi-bin/fb.cgi?A1=start3&A2=Easy&ALG=No&INSTRUCTS=1
Multiplying -Decimals level 2 http://www.funbrain.com/cgi-bin/fb.cgi?A1=start3&A2=Medium&ALG=No&INSTRUCTS=1
Equivalent Fractions http://www.aaastudy.com/fra42ax2.htm
Comparing Fractions http://www.aaastudy.com/fra42ax2.htm
Fractions-lowest terms http://www.fractionbars.com/Lowest_Terms_Game/
More Fractions http://www.funbrain.com/fract/index.html
Multiplying & Dividing Mixed Numbers Fractions http://www.math.com/school/subject1/lessons/S1U4L7GL.html
Multiplying Fractions http://www.math.com/school/subject1/lessons/S1U4L4GL.html
AAAMath-Math Practice http://www.aaaknow.com/grade6.htm
Math Blocks - 4th Gr. http://www.mathcats.com/explore/obbl/obbl.html
Polygon Playground-4th Gr. http://www.mathcats.com/explore/polygons.html
Making a Graph http://nces.ed.gov/nceskids/createagraph/default.aspx
Interactive Georboard (4th-6th) http://standards.nctm.org/document/eexamples/chap4/4.2/part2.htm