There was an excellent episode of NPR's Science Friday this past Friday about how bees communicate and make decisions when swarming.
The show was broadcast just before Christmas and the 200th birthday of Lorenzo Langstroth, the "Father of American Beekeeping."
I was especially impressed with the recorded sounds that bees make during the various stages of swarming.
You can find a transcript of the NPR show here and/or listen to the show on-line.
Here's the link to the MP3 if you want to download the show and listen off-line.
The Science Friday page has links to videos with segments including the "piping" sounds that the swarm produces when the decision has been made about the location of the new home for the swarm.