Cheap AC fan?
 

How cheap can I get a ~120mm AC fan for? I'd like to build an external cooling box that sits outside my computer room, so DC power is out. Noise isn't a huge concern, but ideally I'd like something around 50-80 CFM. I don't care if its axial or radial, just so long as it has a frame so that I can easily strap it to a heatercore.

Thanks for any suggestions.

Look around your area for electronics surplus and parts stores, they'll have AC fans for pretty cheap. You can also use online vendors like MECI and ElectronicsSurplus.com.

MECI AC Fans
ElectronicsSurplus.com

There are other well known online surplus stores but I can't remember them at the moment.

Some places to check online:
Electric Trading Co
MPJA
Goldmine-Elec
Quickar Electronics
All Electronics Corp
American Science & Surplus
Alltronics
Herbach & Rademan
Surplus Center

American Science and Surplus has some (IMO) really good AC Papst/ebm impellers for $12 or so which I'd use in an external box - use the impeller to pressurize the box with the rad(s) in it and let the air flow out through the rads. You'd have to mount the backside of the motor to a plate and mount that so that the impeller lined up with a hole in your case, so not as easy as "strap to a heater core", but maybe similar work if you were thinking of building a shroud or two...

I saw those impellors actually, but they have no caseing so I'm not sure how you would hook them up to a heatercore.

I'll look at those other sites, but I'm starting to think that the best option is to get a wall wart style DC supply since AC fans tend to be extremely powerful and loud.

Well, you either hook 'em up to pull through a shroud (shroud attached to a heater core):
http://koure.org:800/temp/mounted_impeller.jpg
Or you hook 'em up to pull air into your enclosure and let it vent out through the heater core (so the entire enclosure becomes the shroud).
The impeller in the picture is smaller than the one at am sci and surplus - but those will still fit in the same area a 120mm fan will (only a good deal thicker). If you wanted to put a couple of heater cores in the same box, they'd both get fresh air if you ran it this way.
They aren't quiet, but man they have some suction.