SquareOak already posted some info about how to add a Sphinn button to the Share This WP plugin. If you use Social Bookmarking Reloaded, like me, you can add Sphinn to your list like this:
Go to Plugins > Plugin Editor > and click on the social_bookmarking_reloaded.php file. Towards the top of the code is where you can add new bookmarking sites. CTRL+F for “blinklist|” and add “sphinn|” to the list.
Now open sites.xml and add the following code:
Now save this image: and upload it to wp-content/plugins/social-bookmarking-reloaded. Go to “Options” in your WP-admin and select Sphinn in the Social Bookmarking Reloaded section.