Here are some ideas, although many of them might not be practical. Hopefully they'll serve at least as a mental exercise for what is possible.
In order of most practical to least:
*
Swamp Cooler
*
Increased attic insulation
*
Paint roof white
*
Solar Chimney
*
Earth Cooling Tubes
*
Green Roof
*
Roof Pond
Some of the neatest ways of keeping warm in the desert have been around for centuries, the
windcatcher:
Windcatcher
I get the feeling that houses could be designed better if you left a monkey alone in a room with a pen and paper. It's amazing some of the ridiculously poorly thought out buildings architects churn out around the nation.
"Oh, so you want a home in the mountains...how about a ranch style? Oh, the desert...how about a ranch style?"
- LostCause