Writing up a final paper for my Media Management class, I found myself getting interested in the practical aspects of competitive intelligence (CI) for SEO.
I found a page that outlines some interesting "black hat" SEO tactics, with a smattering of other, underhanded ideas:
http://www.seobook.com/archives/000964.shtml
Mostly, I'm just writing this post to bookmark that page for my future reading-and-thinking. Right now, I must run to class and turn in my paper. :o)