Learning Chocolate is a very good interactive vocabulary site for beginning readers. The site is divided into categories, provides audio support for the text, and has numerous re-enforcing online games.

Max's Math Adventuresis from Scholastic, and offers a variety of relatively simple math games.
UpToTen Game and Activity Search Engine
If you’d like to be able to suggest online games and activities that will help young and improve their coordination, logic, or computer skills, then look no further than UpToTen’s search page.
The IBM KidSmart Early Learning Program integrates new interactive teaching and learning activities using the latest technology into the pre-kindergarten curricula.