Is it safe to run a wire through the air vents of my car? Specifically, during the winter when the hot air is going through it. I have my cradle for my PDA on the air vent and wanted to run a constant power wire through the air vent so it is more hidden, but wasn't sure if it is safe.

It would depend on the wire -- you'd have to check the temperature rating for it. (I discovered wires have temperature ratings when installing an overhead flourescent lamp in my kitchen, so this is the sum total of my knowledge on this topic. )