Post secondary schools need experienced people to teach a wide variety of skills.

Debra Wutke, Program Manager for Business Management in the Continuing Education division of Red River College describes the paid and volunteer opportunities for retired people in her college:

Many retirees get satisfaction mentoring young people in their field; an ideal place to pass on your experience is at colleges and universities that hire skilled people on short-term contracts to teach continuing education students, and in some cases, full-time students as well.  Alternatively, colleges often invite experienced people to volunteer as guest lecturers once in a term.