My first recommendation is to step back and ask "what is causing my home to become so hot" (and don't say "because it's hot outside" - two homes in the same neighborhood can have vastly different internal temperatures). By addressing why your home is heating up so much you can get ahead of the game.
Insulation, air flow, windows and orientation all contribute to a house (or a particular room) being 'cool' or 'hot'. Do you have windows that are in full afternoon sun? Cut down on solar gain with drapes, light-colored throw rugs (which will not absorb heat as much as dark tile), or awnings. Is your home well insulated (especially around the roof?)
Finally, take advantage of the cooler periods and cooler rooms in your home. Open the windows at night to cool off the house. During the day, if you have a cooler basement or northern-facing room, open the windows in there and the windows on your top story and use fans to "pull" air from the cool room and "push" it out the top floor. Vornado fans are fantastic, but I've had as much luck using window-mounted box fans set to either 'pull' or 'push' air, and they cost about $20 each new.