At home I use a $10 ventilated seat cushion from the local autoparts store. I figure the open weave allows air to circulate past the hot bottom of the laptop, so it is good for me and good for the laptop. Unfortunately it is too big for air travel but it does double duty when I'm driving.:)
The cheapest alternative I've seen is simply a piece of heavy cardboard folded over once or twice.
--GregB
I use a ventilated car seat cushion folded flat. $10 at your local auto parts store. Keeps me cool and I can sit on it while commuting. Here is an online link: http://ng.shop.com/op/~Comfort_Products_Standard_V entilated_Seat_Cushion_Black-prod-17004563
The cheapest alternative I've seen is simply a piece of heavy cardboard folded over once or twice. --GregB