For those of us that work at home, the third space is really a second space, which I would argue makes them all the more important. We talk a lot about making our places multitask here on Apartment Therapy, which can be essential with limited square footage, but there is also something to be said for finding a third space.
Be it attending classes at a yoga studio instead of practicing in a cramped living room, trading a balcony container garden for a community plot, or just taking your home office to the local coffee shop, finding a third place will give you a welcome change in scenery, a chance to socialize, and help you become more involved in your community.
The concept of a "third space", or "third place", was introduced by Ray Oldenburg in his book The Great Good Place. To learn more about the concept, check out the book, or Wikipedia article on Third Places.