Patrick Robrecht

Posts and Users Stats offers statistics about the content and the users of a WordPress installation:
<ul>
<li>Posts per Publication Date</li>
<li>Posts per Taxonomies, i. e. per category, per tag and per custom taxonomies</li>
<li>Posts per Author and Post Type</li>
<li>Posts per Status</li>
<li>Comments per Date</li>
<li>Comments per Author</li>
<li>Comments per Status</li>
<li>Users per Role</li>
<li>Users over Time</li>
</ul>
All statistics are available as a diagram and as a table (which can be exported as CSV).
After the installation you can find the statistics as subpages of Tools.

Posts and Users Stats

Statistics about the number of posts and users, provided as diagrams, tables and csv export.

Dor Zuberi

The “Right Now” Extended Plugin allows you to decide which statistics to show on your “Right Now” dashboard widget on the control panel. 
You may choose the statistics you want from the following list:
<ul>
<li>Posts</li>
<li>Pages</li>
<li>Categories</li>
<li>Tags</li>
<li>Comments</li>
<li>Links</li>
<li>Users</li>
<li>Media</li>
</ul>
For further information, please visit the official plugin site: <a href="http://www.zuberi.me/2011/right-now-extended-plugin-for-wordpress.html" title="Official site" rel="nofollow ugc">“Right Now” Extended Plugin (for WordPress) | Three Dots</a>.

"Right Now" Extended

The “Right Now” Extended Plugin allows you to decide which statistics to show on your “Right Now” dashboard widget on the control panel.

Posts and Users Stats vs "Right Now" Extended