Discovery Young Scientist Challenge: 
        National Science Fair competition for middle schoolers in grades 5-8.

     http://school.discovery.com/sciencefaircentral/dysc/

Toshiba/NSTA ExploraVision Awards: 
        Contest open to students K-12 who work in teams to explore their vision of future technologies.

     http://www.toshiba.com/tai/exploravision

Craftsman/NSTA Young Inventors Award Program: 
        Contest open to students, grades 2-8, who are asked to invent or modify a tool.

     http://www.nsta.org/programs/craftsman.asp