As far as I know, 120Hz/240Hz/480 etc TVs are still only taking a 60Hz signal (?). If not, then you can set your output to 1080p 120Hz and Bob's your uncle. Otherwise you'd be outputting (max) 60FPS and the remaining frames would be interpolated.
Regardless, any TV that would do frame doubling on any other source will do it for PC.
Whether it'll actually take a 120Hz input I don't know. If you're bored I'd fire off a copy paste email to Sharp/Pana/Sony/Tosh/Samsung/LG and friends and ask which if any models will take 120Hz> input.