1. Laptop feet
2. Stands and props
Alternatively, this "DIY Cheapskate laptop stand" is made from cardboard, making it inexpensive or free.
3. Racks and elevation
4. Electronic surveillancesmcFanControl, a free program for Mac OS that lets you monitor your temperature and adjust your fan speed accordingly. Like jlanier, my computer tends to heat up when I'm watching or editing videos, or playing games, so this is a handle feature to have.
Thank you to everyone for sharing their tips!
So, what household items do you use to prop up your laptop?
(Cardboard stand: Flickr member tomas carrillo licensed for use under Creative Commons. Bottlecap: Flickr member muhammad.u licensed for use under Creative Commons. Baking rack cookies: Flickr member sparktography licensed for use under Creative Commons. Books: Flickr member Steve Wilhelm licensed for use under Creative Commons)