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.

Soli

This plugin allows you to append a signature after every post. Some variables can be used, such as %post_title%, %post_link%, %bloginfo_name%, %bloginfo_url%, and so on. It supports multiuser.

WP Post Signature

Works great for me

This plugin allows you to append a signature after every post. Some variables can be used.

3 Sheep Signatures vs WP Post Signature