I think some of the people who have replied do NOT have experience with the "Quiet Cool" brand of whole house fan (www.quietcoolfan.com). These are not your old fashioned giant louvered hallway fan. They are multiple small room units that make almost no noise. I installed them last year in my house and have been very pleased with them.
These small, individual-room attic fans look like regular air conditioning vents, only square and a bit larger, and placed in the ceiling, of course. You can place them at the door to a bedroom and use them to pull air across the room from an open window. You can select which rooms to turn on, or not. I watch my wireless outdoor thermometer, and as soon as it is cooler outside than in, I crank up the "Quiet Cool's". Even though they are right in the bedroom with you, they make so little noise that you can leave them on all night if you want.
I very highly recommend these. (And I got a miniscule rebate from Cal Edison for installing them.)