Competition Analyzer

Compete.com - With compete.com, you will be able to identify rival search marketing strategies and take your SEO efforts up to the next level. it offers affordable competitive research reports.

Quantcast -Quantcast is the only open interent ratings service. They provide advertisers with audience profiles for millions of websites and services. They invite publishers to participate and demonstrate the unique value of their audiences. The service is free to everyone.
UrlTrends- My UrlTrends is a group of features and preferences that allow you to use UrlTrends faster and more efficiently. After you have registered you be able to watch any url that UrlTrends monitors via My Watchlist, RSS Feeds or by email. One of the newest and most powerful features of My UrlTrends is called My Watchlist. It allows you to see at a glance any of the information that you want to see about all of the urls in the WatchList. Whether you only want to see the PageRank of the Urls, or everything we monitor, you can now do so very easily. Free and paid accounts available.

Alexa -Show charts for competing sites. Provides sites traffic zooming and comparison.
Domaintools- DomainWildcard search of all current/deleted/expired whois domains. Domain Suggestions Engine serves over 10 Billion suggestions a year.
SoloSEO- SoloSEO integrates all the SEO tools you need in one place. You can manage up to 5 websites for $29/month, and additional domains are only $4 more a month. After looking through our features, take a tour of SoloSEO. But don’t leave without signing up for a free trial and actually experiencing it…you’re going to love it!
SeoDigger- Detecting search keywords for which a site is ranked high. With Seodigger.com you can find out for which keywords your site ranks high enough to be in Google Top 20. You can analyze your own sites as well as sites of your competition, using the information obtained for SEO analysis, building a semantic core, finding out how well is a site optimized for this or that search request, and a lot more. Apart from a list of search queries, wordtracker and overture results are also determined (keyword popularity calculated by Wordtracker.com and Overture.com). Data is CSV-exportable.
Googlerankings- Enter the domain or URL of your website to see which are the words and phrases it uses most, see a detailed report on their numbers and density

Site Meter - Site Meter Basic offers a FREE, easy to install tool for sites looking to beter understand who’s ivisting their site, where customers are coming from and where they are going within the site.
Google Analytics- Google Analytics has been re-designed to help you learn even more about where your visitors come from and how they interact with your site.
Piwik - piwik is an open source (GPL license) web analytics software. It gives interesting reports on your website visitors, your popular pages, the search engines keywords they used, the language they speak… and so much more.
StatCounter - A free yet reliable invisible web tracker, highly configurable hit counter and real-time detailed web stats. Insert a simple piece of our code on your web page or blog and you will be able to analyse and monitor all the visitors to your website in real-time! Started off a free site but later charge for advance features.

SEO for Firefox - The award-winning Web browser is now faster, more secure, and fully customizable to your online life. With Firefox 2, we’ve added powerful new features that make your online experience even better.
Xinu - Find out how well your site is doing in popular search engines, social bookmarking and other site statistics