Boy's Life Magazine. For boy in grades 3 - 6 http://www.boyslife.org/
Exploratorium - Explore a wealth of online activities across the science, math, and technology. For boys in grades 3 - 6 http://www.exploratorium.edu/
The Yuckiest Site on the Internet. For boys in grades 3 - 6 http://yucky.discovery.com/flash/
For all the boys who love to write in codes or try to break codes. This site has several different kinds of codes. http://www.secretcodebreaker.com/index.html
Choose your own Adventure....the Media Center has some of these titles. http://www.cyoa.com/main.htm