osiris8

Automatically creates an image banner with the heading of the latest post, for use on web sites or as a signature in discussion forums.
The banner image is contstructed from a template image of any size, on top of which text with a user-selected typeface, color and placement is placed at each time a new post is published (or the latest post is updated).
With the use of the image banner as a forum signature you can provide a way of always advertising your latest post on the discussion forums you frequent. The plugin automatically provides bbCode and HTML appropriate for use as signature code for most discussion boards.

Osiris Signature Banner

Automatically creates an image banner with the heading of the latest post, for use on web sites or as a signature in discussion forums.

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.

Osiris Signature Banner vs WP Post Signature