not talking about ANYTHING personal in the interview is total bunk. Companies want to get to know you and what you do away from work says a lot about who you are - potentially a lot of really positive stuff.
One of the things I've done in my work is look at the resumes and LinkedIn profiles of employees to understand trends in hiring - specifically what the common elements are in the backgrounds of folks that get hired. And aside from looking at the obvious stuff like previous company and university, I look at hobbies and other non-work activities.
I can't necessarily explain the correlation between some of these activities and success at work - I mean the connection between folks who study music and the ability to program - what is it? But it's there. Easier to explain is team sports, especially competitive ones, or endurance sports and performance in a corporate environment.
Now no company will ever require a music degree for consideration for a developer role, or participation on athletics - they would miss out on people like me who can't read music and demonstrate a tragic lack of coordination. But including these types of things on your resume point to some positive attributes that you may exhibit.
Another reason to include some of your non-work activities is that companies like to hire people who are passionate about something. As much as the word "passion" makes me want to gag, a person who enthusiastically pursues a hobby may find similar satisfaction from their work. I mean if you geek out away from the office, you probably geek out in the office as well.
Some caveats however: there are some activities that can elicit strong negative feelings and of course, you should try to avoid making people sad with your resume. I'm not a recruiter anymore, so I am not actively making hiring decisions these days, but I can tell you that if someone mentions hunting or taxidermy on their resume, I'm personally grossed out. And so I am distracted from all the presumably good stuff on their resume. Same with things people might see as controversial.
So when you consider putting hobbies and interests on your resume, think about what those activities might say about you and how they might relate to your career. For example, a few of this things I love to do are trapeze and home decorating. The trapeze might suggest that I am comfortable with calculated risk and am developing relationships that require trust; home decorating might suggest creativity and a meticulous nature. So those are definitely things that are reasonable to include on a resume and things I am comfortable discussing in an interview situation.
In the past, when people have asked whether it's OK to include non-work interests on their resume, my consistent, go-to answer is that companies expect people to have a life outside of work. In the case of activities that reinforce the your personal brand, including them on a resume is a great marketing tactic.