Google

WebmasterFeed.org:

Why Duplicate Content Causes Supplimental Results Halfdeck argues why duplicate content will cause pages to end up in Google's supplemental index
Get Your Blog Out of Google's Supplemental Result Hell Aaron Wall outlines some general advice on how to get blogs out of Google's supplemental index
Discover your links through Google's webmaster central It is now possible to get an in-depth view of backlinks Google has found through their webmaster central
List of the Google webmaster guidelines 31 webmaster guidelines broken into four categories and described in details for better understanding
Google Filters, how to get around them and exploit their loop holes The many Google filters / penalties described along with short guides on how to handle them