A few good math websites for 6th Graders are: http://www.internet4classrooms.com/skills-6th-mathbuilders.htm
http://www.funbrain.com/brain/MathBrain/MathBrain.html
http://www.math-play.com/6th-grade-math-games.html
and another fun one is:
http://funschool.kaboose.com/arcade/math/index.html
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