With today's work from home culture, this is becoming more and more of an issue. I am brainstorming with a sub on this very issue right now.

Some of our ideas include:
Campaigning for a political party
Volunteering for a charity - if you use this as an excuse - actually do some actual volunteering, please.
Attending sports events - if you wife doesn't enjoy them - but be sure you know the score when you get home

For inspiration go to meetup.com and see what's actually going on in your area that you have a real interest in. I also suggest that you actually do some of whatever your excuse becomes on a regular basis.