Prismaker System  
   Produces a construction block system that includes letter, number, and mosaic stickers to enhance the educational value.
   http://www.prismaker.com/

Ritvik Mega Bloks  
   Canadian manufacturer of construction block sets for infants and children to age 12.
   http://www.megabloks.com/

Han Nam Corporation  
   Producing plastic building block toys in Korea since 1990.
   http://www.eckorea.net/hannamcorp

Learning Materials Workshop  
   Designs building toys using hardwood blocks, acrylic prisms, and flexible forms that develop children's thinking and imagination.
   http://www.learningmaterialswork.com/

Lego Company  
   Producer of building blocks.
   http://www.lego.com/

Atco Toys  
   Produces a large variety of building block sets and construction toys. Provides links to sales offices.
   http://www.atcotoys.com/

Kiblo  
   3D building blocks designed for infants and toddlers.
   http://www.kiblo.com/

AfiX System  
   Construction blocks with three dimensional joints. Includes product outline, parts catalogue, and pictures of possible configurations.
   http://www.afix.cz/afix/