How do I open links in Visual Studio in my web browser and not in Visual Studio?

There is an extension that provides this behavior called Open in External Browser. It works in Visual Studio 2012, 2013, 2015 and 2017. (An old version available on GitHub supports Visual Studio 2010.)

Thanks goes to Dmitry for pointing this out in his answer to this similar question.

EDIT: The Visual Studio team is finally starting to work on putting this right into Visual Studio. Status of this feature request just moved from “Under Review” to “Started”.