Good old Sony Vaios!
My lovely Vaio happily runs whilst smother in a duvet on my lap on a sofa for 4 hours of coding in Visual Studio, i'm going to have to pick carefully for my next laptop as this is now an essential requirement of and laptop/notebook I buy.
It has the tiniest of vents about 5cm long at the back and a few slits on the base but nothing more, and fan rarely even speeds up!
Guess all Sonys aren't bad!