In the “how to improve a site ranking or visibility” serie, I forgot to mention SEF plugins available for Joomla. This is not SEO in the strict definition, but anyway it definitely helps for natural indexation. Search Engine Friendly (SEF) is mainly about generating permalinks “more readable”, which finally redirect to the same article ID.  Here are the 3 most known SEF extensions from the Joomla directory:

• sh404SEF: sh404SEF rewrites Joomla URL to a more user-friendly format (SEF URL or URL rewriting). It also manages title and meta tags (with or without .htaccess file). It also claims to be fully compatible with Joomfish, OpenSEF, VirtueMart, Community Builder, Docman, … and all that for small DB query time overhead! From a personal perspective, I had trouble to make it running with Virtuemart and JoomFish at the same time (but there were some leads in the forums to get it working). Check the author’s website.
• Artio JoomSEF: This component will rewrite your Joomla! URLs not to be only Search Engine Friendly, but also to be human easily understandable. It provides support for multilingual sites using JoomFish. You can also fully customize your meta tags or your 404 page. It supports the same 3rd party plugins like Joomfish, VirtueMart, Community Builder, Docman and more… Check the author’s website.
• SEF Advance: SEF Advance is a Joomla SEF component which extends its built-in Search Engine Friendly URL functionality and raises it on a higher level. But be aware that this one costs about 40€. Check the author’s website.

For Joomla 1.0 users (if there are still any alive), you can have a look to the Open-SEF extension.

You may find other useful resources in the Joomla SEF extensions. As always, I’m looking towards your comments.