This site has a little bit of everything, or rather, a lot of everything. A web guide for parents, kids, coaches. Oriented toward kids 10 and under, with lots of games and educational activities on a variety of topics, including baseball. CBS Sportsline presents 25 Shockwave sports games, including 3 with baseball themes. Lots of games, education-oriented and fun for various ages.
Prices are very competitive.
Amazon is a great resource for books on baseball topics.