WordPress Admin Notepad is a plugin for wordpress 3.0+ that allows selected user group to view or edit notes as long as they are logged into admin panel.
WordPress Admin Notepad automatically creates a show/hide notepad toggle at top right corner (beside log out link) so that users can access their notes at anywhere.
WordPress Admin Notepad supports ONLY WordPress 3.0 and above, that is after wordpress added Roles & Capability.
What’s New
<ul>
<li>You can now configure the permission to view or edit the notes for the 4 user levels (editors, author, contributor and subscriber).</li>
<li>You can now save the state of notepad (visible or hidden)</li>
<li>Notepad now supports cyrilic texts</li>
</ul>
Features
<ul>
<li>Allows selected user groups (roles) to edit/view notes at anywhere in admin panel</li>
<li>The toggle at top right corner can be disable</li>
<li>Save the state of notepad (visible or hidden)</li>
<li>Configure the permission to view or edit the notes for the 4 user levels (editors, author, contributor and subscriber)</li>
<li>Size of notepad can be personalized (slim or normal) and will be saved using cookie</li>
</ul>
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WordPress Admin Notepad

Add a Notepad to your admin panel so that you can view or edit note at anywhere.

swedish boy

Add up to 3 notepads to the Dashboard. Great for messages, html and ideas between admins and developers on your WordPress Site. 
Read more on how to use Dashboard Notepads in the FAQ.
New in version 1.2
<ul>
<li>Each notepad is now an individual widget.</li>
<li>User view/edit settings for each pad</li>
<li>Configuration on each widget directly.</li>
<li>Configuration page can disable WordPress widgets.</li>
</ul>
Features:
<ul>
<li>Dashboard Widgetized</li>
<li>Up to 3 different notepads as individual widgets.</li>
<li>Disable other widgets (optional).</li>
<li>HTML support for view mode.</li>
<li>Raw CSS customization.</li>
</ul>

Dashboard Notepads

Add up to 3 notepad widgets to your Dashboard. Disable the default widgets if you like. Great for admins to globally message users.

WordPress Admin Notepad vs Dashboard Notepads