Thinking Blocks, Model Your Math Problems: http://www.thinkingblocks.com/

Place Value Practice:

Two Digit http://www.aaamath.com/g3_12bx1.htm

Three Digit http://www.aaamath.com/g3_21bx1.htm

Specific Place Value http://www.aaamath.com/g3_21cx1.htm#section3

Expanded Form http://www.aaamath.com/g31d_px1.htm

Word Form http://www.aaamath.com/g31e_px1.htm

Mystery Number http://www.starrmatica.com/standalone/starrMaticaplaveValueMysteryNumbers.swf

More Games http://www.toonuniversity.com/flash.asp?err=503&engine=15

Other Helpful Math Websites:
Math Practice: http://www.softschools.com/grades/3rd_grade/math/

Free Math Practice Worksheets: http://www.tlsbooks.com/mathworksheets.htm

Math Help: http://www.aaamath.com/grade5.html

Math Games/Practice: http://www.internet4classrooms.com/skills-3rd-mathbuilders.htm

National Library of Virtual Manipulatives (NLVM): http://nlvm.usu.edu/

Thinking Blocks, Model Your Math Problems: http://www.thinkingblocks.com/

Online Assessment System: https://www.georgiaoas.org/servlet/a2l

Mr. Nussbaum Math Games: http://mrnussbaum.com/third-grade-math/