Games to challenge and have fun! http://funbrain.com
National Geographic for Kids http://www.nationalgeographic.com/kids/
Time For Kids http://www.timeforkids.com
Fun Math Activities http://www.factmonster.com
Virtual Manipulatives http://nlvm.usu.edu/en/nav/grade_g_1.html
A Plus Math http://aplusmath.com/Worksheets/index.html
PBS Kids http://pbskids.kids.us