As noted from a post on MarketingLand -
You can see all the tweets that link to your website, whether or not they include your @username. You can see tweets that link to any specific page on your website. You can see how often Twitter users click on links to your website, or to any specific page.
To do this, go to the new Websites link under Analytics and claim your web site by putting a meta tag in the "head" section of your site. (Typepad users will find this under Design > Head). Once you've claimed your site, you can then see analytics performance on a per-hour or per-day level.
This weblog gets enough hits from Twitter that I'm curious where they come from; the new Twitter tools help that curiosity. If you were managing a brand and wanted to see how effective your twittering was, this is one more measurement tool for you.