Everything you wanted to know about website analytics:
- Google Webmaster Tools Best free tools for analyzing web traffic patterns to your site.
- Spyfu An excellent tool to track your competitor's advertising reach and their cost per click, popular Google Adsense keywords, etc. Very useful for giving you a snapshot of what your competitors are up to and their ad spending, so that you could plan your own response. Note that the free service is limited.
- Open Site Explorer - Very useful web analytical tool to check links on your or your competitor's site. Offers free and pro services.