Gregg

This plugin allows you to change the footer text on the bottom left of the admin page.
Once activated, navigate to the Settings -> nuAdmin Footer and change the Footer text/HTML. You can use html to link to your website, your help desk, your email or anything you would like. If you find the plugin to be useful and would like to donate, you can do so in the Settings.
Here’s a link to <a href="http://www.tripleginteractive.com/blog/wordpress/custom-admin-footer/" title="free wordpress plugin: custom admin footer" rel="nofollow ugc">the blog post on this topic</a> for more information. Future version’s will have much more capabilities.

nuAdmin Footer

This plugin allows you to change the footer text on the bottom left of the admin page.

VirtualRealitySystems

Virtual Signature allows Authors to Append their Custom Signature at the end of the post.
This utility like plugin can be used for custom signature of the author.
It is very useful when you need to use your signature and reduces repetitive work.
<h3>Arbitrary section 1</h3>

Virtual Signature

Virtual Signature allows Author to append Custom Signature at the end of the post.

nuAdmin Footer vs Virtual Signature