Yes, the domain name, sex.com, is up for sale, and is expected to sell for many millions of dollars. It is being offered through sedo.com, a large broker of Internet domain names, and instead of being sold at auction, it is being sold as a negotiated sale. The domain name reportedly sold for $14 million a few years ago.
This domain name has had a notorious history, including being hijacked through identity theft, and the true owner spent a long time in court getting it back. You can read all about the history of the domain in the book Sex.com: One Domain, Two Men, Twelve Years and the Brutal Battle for the Jewel in the Internet's Crown (Volume 2) and the book The Sex.Com Chronicles: A White-Hat Lawyer's Journey to the Dark Side of the Internet.
The deadline to contact sedo, if you are interested, is September 21.