Every major content platform, for example, Twitter, Google, Drupal, Sitecore, Wordpress etc. provide some form of analytics. Google Analytics is one of the most common - it's free and easy to integrate - and provides a surplus of information. I've added some of my own statistics to a blog post here and there, as I measure the site traffic here through it. Again, it's free and easy to integrate with most blogging or website platforms. On a side note, not that easy with Ghost yet.
I've recently started exploring Twitter's analytics engine. I've inadvertently signed up for a business account somewhere, but it's provided me greater insight into my tweets and who sees what, interacts with what kind of tweet/content etc. Looking back through my history of tweets, I can clearly see when I started publicizing my blog posts (and actively blogging).
Quite a difference in tweets and interactions.