Pop-out winshield shades work well enough for the front-end. I was carrying about three pairs of them last year when DD'ing my notch - one pair for the windshield, one pair for the rear, one for the sunroof and one for the door window facing south. Worked pretty good, but it was a PITA to set them all up in a hurry and then collapse/stow them all before leaving.
The tint on the side windows of my T-Bird looks to be 35%, and it does noticably help keep my left arm from getting toasty when I'm headed to work (as opposed to when I have the window rolled down). But, as you said, that's probably a UV light issue more so than thermal heat; it still gets hot as a mofo when the windows are up and the A/C isn't crankin'.
Not to threadjack, but has anyone had any experience with those mirror-like tint films? They're definitely easier to see through because they're only like 35%, but they're harder for folks to see into your car and (theoretically) they look like they'd help cut down on the heat a bit.
Other tint idea: What about those see-through graphic sheets you see all the time on the rear windows of trucks n' SUV's, or on those cars done all up with advertising? There's a few designs out there that wouldn't look too bad on a 'Stang, and (at least on a notch) they would fit the rear just about right. They're harder than heck to see through from the outside, too. Dunno if they do jack for cutting down on light/heat coming into the car, though, and they're not too cheap - like around $100 on average.
Yet another idea: Same material as the above see-through graphic stuff, but what if you could score a few sheets in just plain black? I'm sure someone could get it through a sign-making shop or some custom graphics kinda place. That would be a kinda neat alternative to standard tint, IMO. I've seen small squares of that very material sold at Wal-Mart and such for parents to slap on the rear windows of their car to keep their babies from getting sun-baked...
