Given that my Droid is overclocked, and sometimes I forget to drop the speed before I mount it and start a Nav session, and that I like to keep it charging while I drive (smartphone battery life, amirite?), I sometimes find a very hot Droid in my car. I've experienced some reboots when the battery temps (I assume the CPU also, but we can't get a measure on that with Froyo yet) soared as well. SO...I figured since I can't find a way to mount it in front of my A/C vent, I need to get some kind of airflow going. I grabbed my drill and a 1/8 inch bit and this is what happened:
Yes it could be porettier, but I don't see the holes when the phone is in, so... I also made sure that four of the holse in the little snap-in plate aligned with holes in the back to air will move inside the hollow space behind the plate.
It seems to be helping quite a bit. I could easily reach 60-65 degrees Celsius before, now I rarely see 50. If I remember to under-clock back to stock speed, I hover around maybe 40-45ish.
You just have to be careful to not drill any of the important bits like the tabs for the plate to around the magnet. Unless you want to remove the magnet, that is. In which case, drill away!