I have several heated pet bed type things. I have:
http://www.jefferspet.com/sleep-right-thermal-bed/p/0026294/
(they seem to work okay, but it is self-reflecting, so it doesn't get really warm OTOH, they don't need electricity, so it's great for the car)
http://www.jefferspet.com/lectro-kennel-warming-pads/p/2468/
had these for years. warm heat, not too hot even w/o the temp control. i have one i think i'm going to have to retire, cut the dogs seem to like them
http://www.jefferspet.com/snuggle-safe-microwave-heating-pad/p/998/
work great if the dog will sleep on it, it will stay warm all night. great for the car/shows as it doesn't need electricity, but it won't stay warm for more than a few hours if the dog isn't on top of it
http://www.jefferspet.com/pet-bed-warmer/p/0032468/cn/10002/
boyz got these for xmas last year. i made a little slip cover for them and put it on a time for each boy. nice and warm. Jet's is in his bed and Diggie's is where he naps in the afternoon.
http://www.jefferspet.com/thermo-pet-throw/p/0031789/
looks very promising, but not something i have (yet)
i did not get all of these items from jeffers, but i knew they carried them all. Mostly my older kids just nap on the sofa, chair, etc., but i do have a large foam dog pad. I'd bought an ortho bed for the old lab and when the foam wore out, i just replaced it with the thickest foam I could find at Joann's.