I don't follow the lower divisions. There's nobody down their that stands out? That's pretty surprising given the fact that the smaller guys should have faster hands.
Berto, Gamboa, Guzman, Mijares and Kameda all have exceptionally quick hands. I feel like Calzaghe lost a bit of his quickness when he moved to 175, or it may just be his age, but he didn't look all that quick against Hopkins.
I was thinking pound for pound. Of course the smaller guys have quicker hands - their arms are shorter. If you want to say who's really the quickest, it's probably Calderon then, although his quickness has dropped a bit, but in relation to other strawweights, he's not as much quicker as Berto is with respect to welters or Gamboa is with respect to feathers.
Surprised no one mentioned Roy Jones yet for combination punching. He can still put them together about as fast as anyone. Fast forward to about 2:00 into the video. http://www.youtube.com/watch?v=aY8A_ScR4l4