WordPress.org

Author: Nathan Rice

The Single Post Template plugin adds the ability for your theme to include "Post Templates" in much the same way you can add "Page Templates", allowing you to choose (via a simple dropdown) which post template you want to use, on a per-post basis.

All you need to do, after installing and activating the plugin, is create one or more "Post Templates" in your theme's folder, and when creating or editing a post, choose the post template that you would like to use. If no post template is selected, the default template will be used.