Shortcode Reference plugin for WordPress by bartee will provide a list and details about available shortcodes in your current install.
These codes will provide access to plugin-specific things, like displaying a gallery, or a Google-Map. The downside about this, is that there’s no generic overview of all available shortcodes within your environment. If available in the sourcecode, the documentation will be shown.
Requires PHP version 5.0.0.
Download and info: http://wordpress.org/extend/plugins/shortcode-reference/