SEO

Search Engine Optimization

WordPress

WordPress SEO (Yoast)

http://wordpress.org/extend/plugins/wordpress-seo
http://yoast.com/wordpress/seo

All in One SEO Pack (AIOSEO)

http://wordpress.org/extend/plugins/all-in-one-seo-pack

Discussions

http://foliovision.com/2011/10/24/wordpress-seo-plugins-review
http://foliovision.com/weblog

Joomla!

http://www.highervisibility.com/blog/top-5-joomla-seo-plugin-extensions

Discussions

http://www.cio.com/article/714872/10_Online_Reputation_Management_Tips_for_Businesses#article-header
http://tools.seobook.com/robots-txt
http://www.journaldunet.com/solutions/seo-referencement/outils-seo-gratuits-open-source
http://thenextweb.com/socialmedia/2014/09/04/21-free-seo-tools-instantly-improve-marketing