WordPress.org

Reddit Button is a WordPress plugin that displays - you may not believe it. - a reddit button in your posts.

The plugin does of course feature all the reddit buttons and it is customizable as to where the button will show up in a post and on which posts it shall be displayed. The plugin can also detect if a post is being referred to by reddit and have the button automagically show up on said post.

And if, for some reason, you are not happy with the plugin's decision to show or hide the button for a particular post you can customize its behavior using advanced Reddit Button Post control rock'n'roll!