Open the windows, all the interior doors, and the back door and get a cross-breeze going. Add fans for extra air circulation. And eat popsicles. Sit in the basement. Turn off extra lights. Closing the window shades (especially if they're venetian blinds) to block the sun but still allow air to circulate sometimes helps.
Though to be honest, the way our house is situated (south-facing, in a narrow valley) we get such good cross-breezes that A. we have a large collection of decorative bricks to hold doors open and B. we run the air conditioning an average of one day per year-only in the most awful humidity.
