This is a collection of web sites and articles I have found on the subject of Twitter analytics.  I’ll post new ones to the top, so the list is in reverse chronological order, newest first.

Social Bro — a neat, free analytics application for Twitter users.

Fernanda Viégas and Martin Wattenberg — not a web site on analytics, per se, but on visualization, which is an important part of presenting data from analytics.

Engagement Metrics for Twitter: 5 Measures that Can Deliver Big Results

When Social Media Meet Politics

10 Awesome Twitter Analytics and Visualization Tools