Download the zip file, extract the contents and upload to your wordpress plugin directory and activate the “Simple Disclaimer” plugin.

The plugin by default has a standard disclaimer and a disclaimer for PayPerPost. You can add more by adding the disclaimer keyword and description to the array (defined in the php file)

To add a standard disclaimer put this line in your post: [ disclaimer ] s t d [ /disclaimer ]
To add a PayPerPost disclaimer add this line to your post [ disclaimer ] p p p [ /disclaimer ]
In both the cases, remove the spaces. I have added spaces so that ny installation does not interpret this as a disclaimer, you would need to remove the extra spaces.

Thanks to Broobles for his SimpleTags plugin. The code is almost entirely borrowed from SimpleTags plugin.

simpledisclaimer.zip