Keeping Rooms Cool

I get the afternoon sun in the rear of my house so when temperatures get to triple digits, it heats up the bedrooms. I recently changed the sun shade on my car and instead of throwing the old one away, I attached it to the window frame of the window that gets the most afternoon heat (it was light weight so I just used packaging tape to adhere it to the window frame with the reflecting side facing the window). It works great.
You can also drape them over your car seats so that they don't get as hot (especially if they are dark vinyl or leather).