Essential Wordpress SEO Plugins.

This is my personal essential list.

XML Sitemap Generator

http://wordpress.org/extend/plugins/google-sitemap-generator/

All in One Seo plugin

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

Redirection

http://wordpress.org/extend/plugins/redirection/

SEO Friendly Images

http://wordpress.org/extend/plugins/seo-image/

Canonical

http://wordpress.org/extend/plugins/canonical/

WP Super Cache - Increase Page Speed, read here to learn the importance, web page speed test

 http://wordpress.org/extend/plugins/wp-super-cache/

This one (below) is not free, but its worth 97 USD

RSS Feed Aggregator Submitter

http://www.webtrafficgenius.com/traffic.html

Video on it here RSS Feed Aggregator Submitter