I picked up a $20 piece from the local Target today... it's a cloth cover over a hollow rectangular-tube kinda thing... one side fits 15", the other 17" (supposedly) but it seems to be working alright. It's not so soft that the laptop sinks into it.
Obviously, it's not conducting any additional heat away from the laptop so it won't help cool the laptop... but it does eliminate the instances of getting scorched legs. Maybe I need to be wearing pants while watching TV and surfing the net? 😎