The first part of the visual git tutorial explains how to locally track project files with the git version control system. It shows how to add and commit changes, how to browse the history, revert changes and how to work with tags and branches.
Publish full articles without needing a blog or site. There's no setup or login. Just write your text and Write4net will publish it using your Twitter account.
WordTwit is a plugin that utilizes the Twitter API to automatically push a published post to your Twitter account as a tweet, using the blog domain as a short URL.
BuddyPress is a suite of WordPress plugins and themes which extends WordPress MU and brings social networking features to a new or existing installation.
PostRank claims to measure social engagement, including blog posts responding to someone else, bookmarking an article, leaving a comment on a blog, or clicking a link to read a news item.