The Social Media Tab plugin display on your blog boxes that has links to your profiles on social sites
Let your readers easily share articles without ever leaving your blog.
Some kind of Portable Contacts Delegation based on the awesome OpenID/Portable Contacts Demo by JanRain.
Allows you to spread your blog to 30+ social networks via ping.fm. Now with support for scheduled posts and custom triggers.
Add a Plaxo Badge to your WordPress blog. You can display your Plaxo profile info on your Plaxo badge.