SEO Tools
BackLink Analysis Tools
- Yahoo Site Explorer - http://siteexplorer.search.yahoo.com
Search Phrase Suggestion and Volume Research Tools
Free:
- Google Insights For Search - http://www.google.com/insights/search/
- Google Search-based Keyword Tool - http://www.google.com/sktool/
Paid:
- WordTracker - http://www.wordtracker.com
- Keyword Discovery - http://www.keyworddiscovery.com
Toolbars and Plugins
- SEO For FireFox
- FireBug
- YSlow for FireBug
- Privoxy + Tor - This will let you change your IP address for testing.
- HTTPFox
- LiveHTTPHeaders
Demographics and Analytics
- HitWise - http://www.hitwise.com
- Compete - http://www.compete.com
- Alexa - http://www.alexa.com (Also available as a toolbar)
PPC Research Tools
Free:
- Google Trafic Estimator - https://adwords.google.com/select/TrafficEstimatorSandbox
Paid:
- SpyFu - http://www.spyfu.com
Other Tools
- TouchGraph - http://www.touchgraph.com
If your favorite tool isn't listed here, please let us know. There is no shame in submitting your own tools, but please let us know if you are affiliated with the tool you are recommending.