Feeling cold and lazy?
Try firing up a browser tab or two with a heavy Flash application. That will get your laptop good and hot, then just hold it against yourself.* Now you don’t have to stand up to adjust the heat or grab a blanket!
My 2011 MacBook Air runs a little too efficiently for this trick. Kind of makes me miss my first gen Air… That old bastard was a furnace. It didn’t run well, but damn it, it was great on cold Winter nights.
*Don’t scorch yourself. You’ve been warned. I accept no responsibility for the stupidity of other’s.
The Geek Whisperer 
Overheating PCs are indeed useful when the weather is cold.