Ask PhD committee member as reference In Europe, is it common practice to ask an external member of your PhD committee to be a reference on a resume for job applications?
For academic jobs, I think that an external committee member is a good referee. They have read through your thesis, so they are one of the few people able to offer an opinion on the quality of your research. 
For non-academic jobs, I think Christiaan's answer makes sense, they aren't going to be as interested in your research but more your work-related skills.

Personally, I (UK-based) have used the external examiner of my PhD as a referee in the application for my first postdoc and in a successful fellowship application. 
Not being from the same institution probably looks good.