What is the best free SEO plugin for WordPress?

[Aaron]

What is the difference between the free and the paid versions?

[Sandhiya]

There are most of the the popular and most effective anti spam plugin available wordpress.org. Here are some anti spam plugins for WordPress that are completely free and premium plugins here. These WordPress anti spam plugins help reduce both comment spam as well as trackback spam.

http://wordpress.org/extend/plugins/akismet/
http://wordpress.org/extend/plugins/wp-recaptcha/
http://wordpress.org/extend/plugins/wp-hashcash/
http://wordpress.org/extend/plugins/bcspamblock/

[Neil]

One of the most popular ones that is totally free is All In One SEO

[Harus]

thanks for sharing very nice information .

[Maxinder]

All-in-one-seo is the best SEO plugin

[Asim Ad]

One of the best plugins for the wordpress are given below you may like these it helps to avoid spamming
http://wordpress.org/extend/plugins/akis…
http://wordpress.org/extend/plugins/bcsp…

[Naoma Deer]

There are lot of wordpress seo plugin for free. search it on yahoo.

[Sebastian]

Some of best free SEO plugin for WordPress are
All In One SEO Pack
HeadSpace2 SEO
Robots Meta
Google XML Sitemaps Generator

[Daniel M]

I use these plugins on my blogs.

http://wordpress.org/extend/plugins/all-...-seo-pack/
This one will let you optimise you meta tags for all your page.

http://wordpress.org/extend/plugins/all-...webmaster/
You can use this to verify Google & Bing webmaster Tools. Facebook analytics, alexa etc.

http://wordpress.org/extend/plugins/seo-...tic-links/
This plugin will let you automate interlinking you page with keywords within the articles of your site.

http://wordpress.org/extend/plugins/goog...generator/
An xml sitemap generator.

http://wordpress.org/extend/plugins/wp-recaptcha/
This will add a captcha to the comments box to avoid spammers.

[Hal Smith]

I've used All in One SEO Pack and Yoast and Google XML Sitemaps. I like Yoast, people sometimes have problems configuring it right but it still is the best according to me.

Hal Smith
Urldreamer Consultant