Useful Seo Tools

Duplicate Content Checker

http://www.copyscape.com

Free Keyword Suggestion Tools

http://freekeywords.wordtracker.com/

http://www.keyworddiscovery.com/search.html

Google Adwords Keyword Tool

https://adwords.google.com/select/KeywordToolExternal

http://www.google.com/sktool/#

Domain Tools

http://www.whois.net/

http://whois.domaintools.com/

Google Trends

http://www.google.com/trends?

BackLink Checker Yahoo

http://siteexplorer.search.yahoo.com/