genkisan

<ul>
<li>easily switch on and off through Admin Options</li>
<li>display message without editing theme files (above 1st post or through widget)</li>
<li>display different message to different roles/users</li>
</ul>
Demo: 
<a href="http://ericulous.com/2007/03/09/genki_announcement/" rel="nofollow ugc">Plugin Details & Demo</a>

Genki Announcement

Ryo Uozumi

This plugin allows contributors to upload images, and also allows only administrators to see images uploaded by others.
Contributors can only manage their own images.

True Contributor Uploads Display Administrator

This Plugin is only the administrator to be able to see the images uploaded by others.

Genki Announcement vs True Contributor Uploads Display Administrator