105° is just too darn hot
(That's 41°C for my Canadian friends.)
Since I'm too hot to think of anything else, here are a few things I've learned about keeping cool:
Iced tea is necessary for life in the South.
A hairstyle that's long enought to be worn pinned up is actually cooler than a shorter style, since it stays off the back of the neck.
Wearing bike shorts under a dress is more comfortable than going bare-legged, and is much cooler than pantyhose.
Never leave the house without plenty of drinking water.
Turn off all the lights in the house - not only do they add to the heat, they look hot.
A fan to keep the air moving is a must.
We just installed an exhaust fan over the stove in the kitchen and it's amazing how much cooler it is in there!
The best supper on a hot evening is a chef's salad with plenty of veggies, cold cuts, cheeses, and hard boiled eggs. Or ice cream. ;-)
Cooking on the grill is another option. When Mike grills something, he usually cooks enough to last two or three days.
Speaking of supper - during the winter months we usually eat around 6pm, but since 4-6pm is the hottest part of the day here, in the summer I usually give the kids a snack around 4 and we eat supper after 7.
Bring clothes in from the clothesline before 2pm. Otherwise it's too hot to go out and they don't get brought in until after supper!
Everyone tends to be cranky when it's this hot, so I work extra hard at being cheerful, and try to encourage my kids to do so as well.

The Ladies Against Feminism site has an article by a woman living in Australia, called Hot Weather Homemaking, with lots of other interesting tips.

**Update**
The Queen of Popsickles has posted some absolutely divinely inspired ideas for keeping cool. Go read 'em right now!