I liked the concept of using a CD as the bottom, inspired by Gyrobot, both for drainage and easy cleaning, plus shortening the time to print. So I modified the Cool Birdhouse to take a CD/DVD for a bottom. See Cool Birdhouse for additional info about the design and instructions. (http://www.thingiverse.com/thing:116693).
Kudos to Gyrobot and the Birdhouse Bauble for inspiring the use of CDs! (http://www.thingiverse.com/thing:105561)