Pismo PowerBook with no feet.
Maybe you don't have these issues. Maybe you don't even own anApple Pismo PowerbookG3. But if you do, you might be missing some or all of the littlerubber feet that fit on the bottom and allow air to circulateunderneath.
Both of the Pismo's that I have (my working model and mynonfunctional spare parts unit) have lost them. It's no big deal - thePismo's fan has never cut in, and it has always run cool.
But switching to my12" Powerbook G4 has made me just a little more concerned aboutheat. The 90°F weather we have had around here hasn't helped. Igave my wife my Rocket Fish stand and picked up a Targus laptop standwith twin built-in fans. This gave my mind a little serenity, but asthe G4 is missing it's feet, I thought that I would replace both itsfeet and the Pismo's.
What works for one, may not work for the other. The G4's aluminumbody did not like the epoxy I used, so the search for replacement feeton my G4 will have to wait. I did buy a new cooling pad for it withUSB-powered fans. It does manage to keep the G4's temperature under48°C, but I'd like to create more air space under the body.
Meanwhile, my plan works great with the Pismo, and it should workwith WallStreet andLombard PowerBooks (andpossibly other 'Books as well).
Clean the spots with nail polish remover.
Cheap new replacement feet.
First, flip over your 'Book and look for four plastic indentationswhere the feet used to be. You're going to need to clean out thesespots to make sure the adhesive sticks to the new pads. I raided mywife's cosmetic supplies and used nail polish remover and a cottonswab.
After cleaning the bottom, I used Krazy Glue to attach a set ofreplacement pads that I purchased at the hardware store. Cheap, too.You're looking for adhesive tabs in the housewares department. They aremeant to fit on the bottom of a small appliance. I recommend bringingyour 'Book to the store so you get the right size.
Pismo PowerBook with replacement feet.
Now my Pismo sits above the surface of my desk. If it had a heatingproblem (it still doesn't), there would be more room under this oldPismo for air circulation. 
