If you are considering raising your own chickens you will need a chicken coup, or poultry pen. The following chicken coop and poultry pen plans are free. Consider your chicken coop or poultry pen requirements and available space, then you can either use one of these chicken coup or poultry pen plans or modify one to make it suit your specific needs and requirements.
Plans 1 - 8
Plans 9 - 12
A lot of pictures and information on chicken coops and raising chickens.
The University of Tennessee provides drawings for five poultry houses, two broiler houses, and two dead poultry composting facilities. Good layout drawings but no instructions.

Chicken coop This site provides excellent drawings and detailed information.
This poultry pen is made of PVC pipe and fittings. Very good drawings but few instructions.
Good drawing but no instructions for this hen house.
Excellent instructions, plans and drawings for this chicken coop.