RequestPolicy for Firefox blocks all requests to other domains. I sometimes think it should do sub-domains too. When you use this you will see just how many assets websites load from or place elsewhere.
But sometimes the content will not load at all, because to show an article's text, the page uses Google's ajax, webfonts, a cdn, and the blog's master site @ wordpress.com or blogger.com etc. In that case, the content has to be really interesting for me to allow all those third-party connections.
I really, really wish there existed versions of RequestPolicy and NoScript with large and comprehensive default whitelists. Until that day, Ghostery is all that I have the patience to put up with.