I just found this great list of SEO tools on the Yahoo store site and wanted to share the information. Here it is:

Ranking Checkers

• Digital Point: http://www.digitalpoint.com/tools/keywords/Digital Point offers a great free tool for checking your rankings on Google, MSN and Yahoo. Google rankings require you to get a free Google API key. MSN and Yahoo rankings require your to place a small PHP script on any publicly accessible server running PHP.
• Word Tracker: http://www.wordtracker.com/ Word Tracker is the industry standard professional (paid) tool for tracking your rankings and identifying new keywords to target. There are free tools that perform most of its functions, but for the fee Word Tracker places some good tolls in one location.

Other SEO Tools

• Go Rank: http://www.gorank.com/seotools Great tools for analyzing keyword density of your site vs. top 10 results in Google.
• SEO Toolbar: http://www.seoinc.com/toolbar/ SEO Inc. has a toolbar similar to the Google toolbar that provides lots of useful information for SEOs including backlinks for Google, MSN, Yahoo and AOL.
• DNS Stuff: http://www.dnsstuff.com/ DNS Stuff is a great collection of DNS lookup tools including whois, reverse DNS lookup, IP whois, smap database lookup, IP location lookup and more.
• Rick Swain's HTTP Viewer: http://www.rexswain.com/httpview.html Lets you view the header for any web page. Great for seeing what kind of redirect is being used, what server it is running on, etc.
• SEO Tools: http://www.webconfs.com/
• Macdar: http://www.mcdar.net/ Mcdar has several SEO tools including link popularity checker and keyword analysis tools.
• Li'l Engine: http://www.lilengine.com/ Li'l engine has some nice SEO tools including link popularity checker, backlink comparison tool and PR checker.
• SEOMOZ: http://www.socengine.com/seo/tools.php Lots of good SEO Tools. Also good articles for advanced SEO here http://www.socengine.com/seo/advanced.php.
• Yahoo Search Marketing (formerly Overture): http://searchmarketing.yahoo.com/rc/srch/ Use their Keyword Selector Tool to find out how often keywords are searched and their View Bids Tool to see how competitive they are.

Please let me know if you suggest other tools to add to this list.
Thanks,
Kathy