Because I've had issues installing other social bookmark plugins, I'm currently using Social Bookmarking Reloaded, and thought I'd see if I could add Sphinn to it. Luckily, it was easy, so my goal was accomplished. I've packaged the plugin up so you can have the revised version as well. Just click here to grab the revised version. See the original creator's site for any help or info you may need about the plugin.
(See the little icons right under this post? That's this plugin in action).
An hack has been released with few more site added.. >>
http://www.tech-resource.info/article/329/social-bookmarking-reloaded-for-wetogether