One very important blog - if you haven’t found it - is Matt Cutt’s blog. Matt works at Google and has become the primary interface between Google and the SEO community. This is as close as you are going to get to the inside scoop on how Google works. You can find his blog at:
http://www.mattcutts.com/blog/.
Check it out - search by topic or scan the archives.
A good recent posting is available at:
http://www.mattcutts.com/blog/infrastructure-status-january-2007/
This describes some of where Google is going in 2007. It’s a little big of technical stuff here, but those supplemental results he mentions are the listings Googe returns when it can’t find enough information on a search in its main database. These are labeled as such in the return from a search. Obviously, that isn’t a good place for your site to be listed. If you are there, it generally means you have a weak image to the search engine (too few links to your site?) or you are doing borderline spamming of the search engines. Matt says it basically means you have low PageRank.