Are you still active in research & in need of support? If so, learn about OSCAR
Center for the Arts: Become an usher (12 performances per year commitment) & see them free: http://firstname.lastname@example.org
Become a member of the GMU speakers bureau: https://masonspeakers.gmu.edu/faculty-staff-participation-form/
Give talks at RFA events . Please contact program chair with details: email@example.com.
Give talks (or a whole course) at the Osher Lifelong Learning Institute, http://olli.gmu.edu/
Become a marshal at the graduation ceremonies: http://firstname.lastname@example.org
Help out during welcome week: http://welcomeweek.gmu.edu/volunteer/
Help your former department by becoming a mentor or advisor, and maybe get some office space in the process?
You could also become a tutor: https://learningservices.gmu.edu/
For tutoring specific subjects you should contact the department chair
Other mentoring opportunities for students and faculty: