Starfall http://www.starfall.com
National Geographic for Kids http://www.nationalgeographic.com/kids/
Learn how to build numbers up to 999 with this fun, interactive base ten blocks game. http://www.learningbox.com/Base10/BaseTen.html
Watch real scientists in action! http://pbskids.org/dragonflytv/scientists/index.html
Practice place value with this cool shark game! Have fun! Shark Pool Place Value