It's always interested me in my travels and meeting educators at International Schools across the world how many teachers are also entrepreneurial types with some kind of business in addition to their full time teaching job.
Generally the people I have met who this applies to are in Education Technology, whether as ICT teachers, school IT Directors and staff, eLearning managers and classroom technology experts etc. Of course this could apply to other teaching areas equally but as an EdTech guy these are mainly the people I meet the most :)
The most common side project I have come across is with several teachers I know in Europe who organise conferences or training events. Some IT Directors do consulting work for other schools, such h as IT Department audits and I know a teacher in the Netherlands who has developed several IPhone Apps which give him a decent side income.
There are completely unrelated businesses that teachers also run. Many Teachers in I have met in Bangkok seem to do this for some reason. I know one teacher there with a Subway franchise, and a good friend of mine in Bangkok definitely wins the award for being the 'Richard Branson of teachers'. He has a bunch of businesses across Asia, from manufacturing in Japan, sourcing products in China, social entrepreneurship project in Burma to tea growing in Malaysia. Truly I have no idea how he fits it all in.
My opinion of teacher entrepreneurship is that it is fantastic and translates to more real world experience to pas on to the students. Detractors would say outside work is a distraction from the role of teaching, and indeed many school contracts forbid outside work, paid projects (hence why I haven't mentioned any names here), but I think this is a huge mistake. My argument about that is the teachers who do this generally have a very systematised approach to their work (you have to when you have a full time job as a teacher), wither it can run passively without them, on for things like consulting and training it can take place in the holidays.
I also feel that International School teaching by the very nature of the job attracts more adventurous types who are more likely top have an entrepreneurial side.
Definitely interested to hear the perspectives and opinions of teachers in this group.