Google, combined with good SEO can help you tremendously when trying to determine how your competition is ranking well with their web sites. Furthermore, understanding basic Search Engine Optimization will help your blog or site rank higher in the search engines. What follows is a list of terrific sites and tools that will help you understand what your competition is doing as well as optimizing your own site for higher rankings. These resources can be a tremendous help to you in marketing your ebooks and digital products online.

Google Webmaster Central
http://www.google.com/webmasters/

Vaughn’s Google Search Engine SERP Ranking Factors
http://www.vaughns-1-pagers.com/internet/google-ranking-factors.htm

The Seomoz Ranking Factor Page
http://www.seomoz.org/article/search-ranking-factors

Fast Blog Finder Helps To Locate “FOLLOW” Blogs In Your Niche. Posting comments in blogs with “NOFOLLOW” attributes will not give your site any link juice by posting comments with your URL there. This utility helps you find blogs, that because they do ont use NOFOLLOW tags, which can provide link juice to your site.
http://www.fastblogfinder.com/

Courtney’s Site With Tons Of Tips For Generating Backlinks
http://courtneytuttle.com/2007/04/09/102-ways-to-make-your-blog-or-site-a-back-link-superstar/

The Firefox NoDoFollow Plugin
This plugin shows you wish links on a page are Follow and which are NOFOLLOW. Extremely useful when looking for places to post your links to get some linkjuice for the search engines.
 https://addons.mozilla.org/en-US/firefox/addon/5687

SEO Quake is another extemely useful SEO plugin for Firefox
http://www.seoquake.com/