WP Post Signature is a plugin by Soli that allows you to append a signature after every post. Some variables can be used, such as %post_title%, %post_link%, %bloginfo_name%, %bloginfo_url% …
Requires WordPress Version: 3.0 or higher, Compatible up to: 3.1.2
Download and info: http://wordpress.org/extend/plugins/wp-post-signature/