Blase Beczkowski

It is a plugin that adds two sidebar to the dashboard of the admin panel and specjal DW Text Widget. You can place any widget in your dashboard. The whole styling is done in such a way as to keep the appearance of the administration panel in harmony. 
You can use it to leave messages or other information to all users or only for specific roles or specific user.
Thanks for downloading my plugin. I hope it will serve you well and meet your expectations.
I wish you successful cooperation.

Dashboard Widget

Very simple plugin to add sidebar with custom widget to your dashboard. You can add a sidebar which is only available to authors.

Aaron Butacov

This plugin allows you to add whatever you want to the WordPress dashboard through PHP and HTML even Sidebar Widgets. You can also wipe the entire dashboard or individually remove some of the more irritating sections like the Dev news, Planet WordPress and the getting started section.
In WordPress 2.5, the code is cleaner, the plugin is more responsive and you can add both “real” sidebar widgets, or add “fake” ones to match the dashboard.

Dashboard Editor

With this plugin you can remove sections of the dashboard, add new code, or even add Sidebar Widgets.

Dashboard Widget vs Dashboard Editor