Today, I sat in on the second part of a two-part series on SEO by Jonathan Hoekman.  Much better than the first - covered much more useful information about on-site and off-site optimization.  More specifically, the importance of sitemaps (both txt and xml), robots.txt files and why you would want to block certain pages, internal linking, url structure and much more.  It really has quite a bit of useful information especially if you are new to SEO.