I really really really want a birdhouse mounted on a post, so i have been looking online for plans. I stumbled on this info, thought I'd share :)

http://www.holoweb.com/cannon/buildingbh.htm

and some plans:
http://www.choosefreedom.com/birdhouse.html (i think i like this simple design the very best)

http://bygpub.com/bluebird/ (gee, just a kit would make my day!!)

http://www.conservation.state.mo.us/nathis/woodwork/ww6/ like an apartment complex for birds!!