My MacBook averages around 52-55 C (125-131 F) with the fan at 3K.
I have seen it go as high as 88 C (190 F) with the fan roaring around 6K+ when doing a disk permissions verify or using Handbrake to rip DVDs. I never like to see my temperature go that high and I always expect there to be a problem, but i've never encountered any problems. It can't be good for the longevity of my MacBook though.