Copy large files to multiple machines on a LAN

I have a few large files that I need to copy from one Linux machine to about 20 other Linux machines, all on the same LAN as quickly as is feasible. What tools/methods would be best for copying these files, noting that this is not going to be a one-time copy. These machines will never be connected to the Internet, and security is not an issue.

Update:

The reason for my asking this is because (as I understand it) we are currently using scp in serial to copy the files to each of the machines and I have been informed that this is "too slow" and a faster alternative is being sought. According to what I have been told, attempting to parallelize the scp calls simply slows it down further due to hard drive seeks.

BitTorrent. It's how Twitter deploys some things internally.

http://engineering.twitter.com/2010/07/murder-fast-datacenter-code-deploys.html (web archive link)

How about UFTP, it uses multicast to deliver files over UDP to multiple clients at once. Not for everyone and I'm no expert on it but it sounds like it does what you want.

Have you tried to copy this data with rsync? If you have 1 Gbit LAN or faster, copying over 4*20 GB should not be a problem.

How often will this copy occur? Does it matter if it takes couple of minutes to finish?