Privacy Badger (https://www.eff.org/privacybadger) blocks a bunch of stuff on StackOverflow.
Blocks Scripts:
www.google-analytics.com
edge.quantserve.com
b.scorecardresearch.com
Blocks Cookie Only:
ajax.googleapis.com
www.gravatar.com
i.stack.imgur.com
Blocks nothing:
cdn.sstatic.net
Add content relevancy is one part of the equation, but not allowing third parties to track my actions on your site is the other, more important part of the equation (to me at least). Privacy Badger is the only adBlocker I use (besides having flash not run automatically), so I will happily view ads that don't involve tracking me.