These amazing 12 free games would be great for interactive whiteboard or laptop. I've played a few of the. I love #3 which lets you teach coordinates. You can choose one quadrant (x,y - positive numbers only), 2 quadrants (xy - positive and negatives) or 4 (xyz positive and negatives) - great game for reinforcement.
All of the games are math / numeracy games so spread this like crazy for your math classes. TES is a great site out of the UK for free stuff and is the largest network of English speaking teachers in the world.
Big list of flash-based activities, games, and interactives that work well for use with an interactive whiteboard in a mathematics classroom. Includes many areas of math including geometry, numeracy, fractions, probability, and more.
Turtle Diary is a wonderful, must try site packed with a huge collection of online interactive games and activities for young children, including maths and literacy resources.
http://ictmagic.wikispaces.com/Early+Years