I keep my resume in an OpenOffice OTP file and also maintain a LinkedIn profile. When I am ready to look for a new position, I'll update the resume using information from LinkedIn since it keeps track of things like duration and employer information pretty easily. From there, as I look for jobs, I'll customize the resume based on the new employer and what they are looking for, export in a format that they can read (usually PDF, especially if they don't specify anything), submit it, and move onto the next job listing
This page is the first time I'm hearing of JSONResume. Honestly, it sounds excessive and only useful for applicant tracking systems (which can be useful if you're in an industry that's ATS-heavy, which mine is not)