Until this morning, I had never heard of a splog. I thought it was some hip new social media network that had been kept a secret from my every roving cyberspace eye. It was interesting to discover that a splog (realizing now that I've seen them before) is spam at it's worst!
A splog (spam blog) is a fake blog created solely to promote affiliated Web sites, with the intent of skewing search results and artificially boosting traffic. Some splogs are written like long-winded ads for the Web sites they promote; others have no original content, featuring either nonsense or content stolen from authentic Web sites.
Splogs include huge numbers of links to the Web sites in question to fool Web crawler s (programs that search the Web for sites to index). The sploggers associate popular search keywords with their pages so that the splog links turn up in blog search results and are sent out as search subscription notifications through e-mail and RSS feeds.
There's a great post here and here about splogs and some things you should know about these site.