This sidebar widget provides a list of authors, useful for multi-author blogs.
Yes, it is, in the older widgets plugin releases. For some reason, the "Authors" widget was removed for WordPress-2.2.
There are many requests for:
The wp-authors plugin simply calls
wp-includes/author-template.php. The lack of all of the above feature requests are due to the sparseness of that API. Implementing any of the above features will require either hacking the WP core or directly embedding SQL queries into the plugin. Both strategies subject the plugin to breakage with each WordPress release.