Im currently a full time student so I really only work on the weekends but I average around 15-20 hours per week.
When I work overseas, I average 14-16 hours a day.
I'm a freelancer, so I really only work when someone calls. I've had whole months without a day's work, and months where I work nearly every day. Most are somewhere right in the middle. Depending on the setup, it's overtime after either 8 or 10 hours a day, and 40 hours per week.
Until recently, this setup was awesome, until the company I did most of my work with got gobbled up by another company and most of the projects got shut down. I still prefer the freedom involved.
We have to sign in before 8.30 AM and sign out after 4.30, so nominally work a 40 hour week. The actual hours of work we do can vary from a few less to quite a few more. As a teacher at a university for the hoi polloi in a partially developed country, I am contracted to do 18 contact hours per week, and have had 150 - 250 students on my rolls. Being fairly diligent, each contact hour can involve an hour or two or more of non contact time.
Like most of my colleagues, I spend very little time in our dreary artificially lit, air-conditioned office on campus. I prefer do my preparation and marking in my apartment, with good natural light and airflow, about five minutes away by bicycle.