Many organizations at Harvard have their own series of public talks. Examples are:

• Forums at the Institute of Politics (part of the Kennedy School of Government)
• Talks at the Radcliffe Institute for Advanced Study
• Norton Lectures featuring award-winning writers, musicians, filmmakers, etc.
• Distinguished Lecture series at Institute for Applied Computational Science (open to public, but intended for a technical audience)

There are probably many more events run by Harvard's other individual schools, departments, and institutes.