BackYardChickens.com has a wide variety of free chicken coop blueprints to suit most needs, which are mostly user-submitted, as well as instructions for incubators, brooders and other chicken needs. About.com also offers a comprehensive list of online resources for DIY chicken coops.
Building chicken coops is a fairly simple and rewarding weekend project. Before deciding on a chicken coop blueprint, first determine what type of chickens you will be raising, as different breeds may have individual needs. Determine what type of space you are working with and how large you plan to build the coop.
Understand the budget with which you are working, and attempt to stay within that constraint. You can save money by using recycled materials and not overbuilding with unnecessary materials. Try to find a blueprint for a simple coop that is easy to clean and maintain, and remember to give your chickens adequate space for roosting, exercising and nesting. Remember to give yourself plenty of time to work on the chicken coop, and plan ahead for any delays, costs or issues that may arise during construction. You should have a basic knowledge of carpentry and woodworking and a good understanding of breed-specific needs for the coop.