Well... the drive out to the observatory at Kitt Peak is nice.
The Pima Air Museum is cool if you like airplanes and the Titan Missile Museum at Green Valley is very cool.
Saguaro National Park is quite fascinating for the all the cactus you can see... provided it's open what with the US government budget problem at present.
If you can, the visit to the "boneyard" at Davis Monthan AFB is fascinating.
There's an abandoned mission church at Tumacacori (just South of Tucson) that's quite photogenic.
Some shots from our last visit are here...
Tucson - a set on Flickr
Have a good trip!