Google XML Sitemaps Generator – creates a sitemap of all articles on your WordPress blog. Helps Google and other search engines index every article you write.
Permalink Redirect – replies a 301 permanent redirect, if requested URI is different from entry’s (or archives) permalink. It is used to ensure that there is only one URL associated with each blog entry.
All in One SEO Pack – Optimizes your WordPress blog for Search Engines (Search Engine Optimization).