rob1n

This plugin does two things to your dashboard:
<ul>
<li>The WordPress News and Other WordPress News sections are removed. You don’t even load them. Why? So you won’t have to bother 
with the AJAX call for the news. Also, it looks neater.</li>
<li>The sidebar (with incoming links, recent posts, etc.) is made more horizontal, with four columns instead of the default one. 
This makes it so you can see all the information at one glance, rather than having to scroll down.</li>
</ul>

Cleaner Dashboard

Removes the WordPress news sections and reorganizes the sidebar for maximum screen usage. See the screenshots for more details.

John Ellmore

This plugin allows the website administrator to remove the following from the WordPress Administration Panel:
<ul>
<li>menu links (like “Tools”, “Appearance”, or annoying menus from third-party plugin)</li>
<li>submenu links (like “Users > Your Profile”, “Tools > Available Tools”, or annoying menus from third-party plugins)</li>
<li>and dashboard meta boxes (like “QuickPress”, “Other WordPress News”, or annoying meta boxes from third-party plugins)</li>
</ul>
It relies on hardcoded settings in wp-config.php (instead of having yet another admin settings page to deal with). Since the settings are all hardcoded, it can be easily set up by a website administrator and left in place without any users messing with it. It works on both single and multisite installations.

Simplify Admin Panel

Allows easy removal of menu links, submenu links, and dashboard widgets from the WordPress Admin…

Cleaner Dashboard vs Simplify Admin Panel