Boxes and Arrows has a new article on sitemaps and site indexes:

How do you know if your site needs a sitemap or a site index, or both? On very small sites, it is unlikely that either would be needed. Most likely the global navigation can provide direct access to all areas of the site. Most medium- and larger-sized sites should probably include at least a sitemap. Text-based sitemaps require few resources to create and maintain and can provide big benefits for your users. Unless your site is a directory like Yahoo!, a sitemap is the only place where a user can see all the categories and top subcategories in a single place. This is especially important if your site navigation uses expanding and collapsing menus that hide options until a mouseover. Ecommerce as well as informational sites can be improved with a sitemap.

Most medium- and larger-sized sites can also benefit from an index of some type. For extremely large sites, it would be unrealistic to include absolutely everything in the site index. It would simply be too large to use efficiently. Only the most important and most used information should be included. Informational sites benefit more from a site index than the average ecommerce site because the content is generally richer on an informational site. However, ecommerce sites with%2

...via elearningpost