There are many ways WordPress can integrate into social media services and networks, and many ways you can integrate those same services and networks into your WordPress site.
You can also integrate Google Maps, Google Docs, Flickr, Tumblr, and a lot of other goodies into WordPress.
There are many WordPress Plugins that make the job easier, but this article is focused on how to do it manually both for the self-hosted version of WordPress as well as WordPress.com.
- Your WordPress Is In My Facebook — Blog — WordPress.com
- Facebook Integration — Support — WordPress.com
- Publicizing your blog posts
- Sharing — Support — WordPress.com