3sheep

The plugin allows you maintain a number of separate signatures that can be added into posts and pages using short codes.
You can use ‘Number of Signatures’ option to set the number of available signatures. You can then enter each signature using text and variables to add author information. The available variables include:
<ul>
<li>%LOGIN% – Login name</li>
<li>%FIRST% – First name</li>
<li>%LAST% – Last name</li>
<li>%NICK% – Nickname</li>
<li>%EMAIL% – Email address</li>
<li>%URL% – Website</li>
<li>%DESC% – Description/Bio</li>
</ul>
To include a signature into a page or post use the shortcode shown next to the signaure (e.g. [tssig id=”2″]).

3 Sheep Signatures

Allows adding a custom signatures to posts and pages using shortcodes.

David Anderson / Team Updraft

This plugin adds a configurable signature to all outgoing emails from your WordPress site.
<h3>License</h3>
Copyright 2012- David Anderson
MIT License:
Permission is hereby granted, free of charge, to any person obtaining 
a copy of this software and associated documentation files (the 
“Software”), to deal in the Software without restriction, including 
without limitation the rights to use, copy, modify, merge, publish, 
distribute, sublicense, and/or sell copies of the Software, and to 
permit persons to whom the Software is furnished to do so, subject to 
the following conditions:
The above copyright notice and this permission notice shall be 
included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, 
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE 
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION 
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION 
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Add Email Signature

This plugin adds a configurable signature to all outgoing emails from your WordPress site.

3 Sheep Signatures vs Add Email Signature