Yes, I found a version of My December that Josh Groban did in concert, apparently in 2006.
Here it is, right here.
http://www.youtube.com/watch?v=Ew-kk5Xt4PsInteresting. He does a pretty good job, he can belt it out, but I think he's a bit too nosy for the song, plus it was made into a virtual theatrical production. I think Chester's softness and the overall simplicity Linkin Park gives it is still the best by a mile.
Here's a 2007 version Linkin Park did, which I think is really awesome.
http://www.youtube.com/watch?v=wFL9Zj5Gpso