I like Bakfiets types (box bike), the load area in front, the front wheel put a meter or so ahead of the load, and steered by a linkage rod..
http://larryvsharry.com/wp-content/u.../09/family.jpg
people have cut up regular bike frames and added some steel tube from a industrial tube supplier and made their own..
Long tails move the rear wheel back then the load is split in 2 and balanced.
Xtracycle Cargo Bikes
also something that can be bodged together with old bikes additional materials and welding..