I’m currently looking for some Joomla extensions to manage SEO aspects of a website. By default, you already have some pretty SEF configuration bundled in Joomla 1.5. But the native version seems quite limited about metadata and sitemap generation. So I took a look on the Joomla extensions directory and here is the first results I’d like to share:

• JoomSEO: JoomSEO is a Search Engine Optimizing(SEO) bot making Joomla content more Search Engine Friendly(SEF). JoomSEO dynamically creates meta keywords, meta descriptions, changes the title on the fly (Adds the sitename for Joomla 1.5), adds heading tags to content titles and more.   This seems to me a pretty good start point. Check the author’s website.
  
• Joomla 1.5 SEO Patch: This component can improve the SEO settings of Joomla 1.5 with this free SEO patch for Joomla 1.5. The patch allows you to gain fully control over the html head section, the META and title settings in the http header settings in Joomla 1.5 generated pages. Check the author’s website.
• Joomap: Joomap is a sitemap component for Joomla that shows the normal Menu Structure, Content Categories, Sections and Virtuemart Categories in a hierarchical tree or a Google Sitemaps list. It can support all your content along with localization. Check the author’s website.
• Xmap: Xmap is based on the Joomap component. It allows you to create a map of your site using the structure of your menus. Check the author’s website.

I still have to look deeper the difference between Joomap and Xmap, but I think I’ll definitely try the JoomSEO plugin.
If you want other kind of extensions related to SEO/SEF/Sitemaps, have a look to Joomla Extensions for SEO & Metada and Joomla Extensions for Sitemap.
You can also find some tutorials and informations about SEO with Joomla on http://www.joomlaseo.net.

If you have other resources or extensions, feel free to share