some of you guys have probably thought of this already. but as for anyone who hasn't, a lot of people with smaller grows use pc fans for intake/exhaust. at the recycling center in my area there are always computers people have brought in because a part broke or just because they got a new one. they don't mind if you go in and reuse that stuff. something i've thought about posting before and finally got around to it.
bingo. i did this a year ago when i had a small indoor grow. i found about 15 fans ranging form 60mm all the way to 300mm.