I've installed a couple of the big belt-drive fans typically found at Lowe's or HD. They do a great job of exhausting hot air and pulling in cool evening air. They are noisy, however. You can hear the roar in the whole house. They are also big energy leaks in your ceiling. You'll feel hot air coming down in the summer, and lots of warm air will escape in the winter unless you cover it.
You'll probably need to increase the amount of exhaust vent area in your attic, too. The typical attic can't get rid of the air fast enough for the fan to be effective. We added 8 more roof vents along with gable vents at each end of the house.
Installing the fan is relatively easy. In my case, both places had a rough-in framed in the ceiling for the fan. If you need to frame for a 30" or 36" fan, you'll need to cut one joist, and reinforce the opening. I believe the fan instructions included framing suggestions, but I wouldn't approach this without some thought and expertise.
There are some high-dollar whole house fans out there that don't require alterations to the framing, and they have lots of insulation and powered, energy-saving doors. They don't move nearly as much air as a big fan, but since they use multiple smaller fans (like computer fans), I suspect they are quieter. Search Google for 'whole-house fan' and you'll see a bunch of them.