[Delphinus]

All shapes and sizes and cheap. Yeah, my AC fans are loud, but the ones I have are absolute beasts, moving a fair bit of air. I think I paid $12 or maybe $15 each for them.

The DC fans are generally pretty quiet. But what's really keen about the DC ones is that if you use one of those multi-voltage wall-warts like is mentioned above, you can slow down the fan by switching to a lower voltage. Actually that's a really keen idea I never thought about that until I read it in this thread! But that's all the Icecap fans do, they just come with a thermocouple so that they can step down their voltage on their own.

Princess Auto has fans as small as teeney-weeney, to itty-bitty, to average, up to FRIGGIN' HOOOGE!! And blowers too. I bought this teeney-weeney 1" blower there once. I haven't the foggiest what I'm going to use it for yet, but it was just sooo cute! I had to have it.

If you want to go with AC fans (hey, hard to beat the convenience of just plugging them in, no worries about a DC power supply), you can get them there too, or, you might be better off going to a hydroponics outfit (go to Bumper Crop or Harvest Garden, both are good bets for this sort of thing), the fans they have look exactly the same as what I got at Princess Auto (110V AC version), but they're quieter. A little more expensive though, but it might be worth the investment if they make less noise than the surplus industrial beasts that I've got...