DIY Chicken Coops

Now that I've got approval from my landlord to keep a few hens (I would like 4), I was wondering about good resources for designs/plans/blueprints. Where did you come up with your ideas? Any book recommendations?
Some of my concerns are safety (we've got large and crafty raccoons here in Philly), comfort (in terms of winter warmth/sun exposure and ventilation), and aesthetics.
What kinds of successes (or failures) have you experienced in your backyard?