The single best source for quality information on salt production is the series of proceedings of International Salt Symposia co-sponsored by the Salt Institute going back to 1966.
For those interested in overviews and summaries, the following offer great choices:
"Salt Mines " -- one of the "Modern Marvels" series on The History Channel.
"Salt " -- another of the "Modern Marvels" series on The History Channel (release: December 2008)
"Salt " -- one of the "How Stuff Works" series on The Discovery Channel (release: January 2009)
"Salt of the Earth " -- Smithsonian Magazine (release: 1999)
"Production " -- MR BLOCH ARCHIVE
"Production " -- Salt Association (UK)
"Salt " by Rose Secrest on Encyclopedia.com
U.S. Geological Survey publications
UNICEF has collected valuable information on technical questions involved in producing iodized salt
International Society for Salt Lake Research
Global Network for Environmental Science and Technology
Solar saltworks - an environmentally friendly industry by Joseph S. Davis
Video: Discovery Channel's How Stuff Works: Solar salt production
Compass Minerals/Salt Union Winsford mine (UK)
"Salt Miner" episode in tv.com's "Dirty Jobs" (February 27, 2007)