Yoga studio or dance space: A clean space with appropriate flooring, mats, bars, and a sound system. You might need to hire a flooring contractor to install proper flooring for these activities.

Greenhouse or potting studio: You will likely need to work with putting in more windows, grow lights, and work stations for tools, soil, and plant material.

Office space: Again, make sure you also have good security, but your garage could be made over to support a business, a writing career, or the student(s) in your home.

Source: http://www.networx.com/article/fabulous-uses-for-a-garage