Here’s some of my bookmarked reading sources for SEO

http://www.searchengineoptimising.com/link-building

http://www.searchengineoptimising.com/link-popularity-explained

Of course you can’t miss out Google’s Webmaster Tools/Guide

http://www.google.com/support/webmasters/bin/answer.py?answer=35769

and there is also Yahoo! Search Content Quality Guidelines…

http://help.yahoo.com/l/us/yahoo/search/basics/basics-18.html

MSN Live’s Bing Webmaster Center Tools and Guidelines
http://help.live.com/help.aspx?mkt=en-us&project=wl_webmasters