Some info on the dark side of SEO - proceed with caution.
http://www.bruceclay.com/blog/archives/2008/06/smx_advanced_goes_dark.html

Some new seo info from Matt Cutts
http://www.mattcutts.com/blog/improved-seo-documentation-galore/

3 ways to spy on your competition.
http://searchenginewatch.com/showPage.html?page=3629807