PHDcomics challenges you to describe your thesis in two engaging minutes through their Two-Minute Thesis contest. Harvard Astronomy students may create similar videos, or submit a winning entry to the contest to have the narration animated by Jorge Cham.
A past example from astronomy is "The Secret Lives (and Deaths) of Stars": Hold onto your stellar companions! Ph.D candidate Or Graur (University of Tel Aviv/American Museum of Natural History) tells us what he's learned about the violent star-deaths known as Type Ia supernovae in this month's edition of PHDtv's Two-Minute Thesis series. (More videos at: http://www.phdcomics.com/tv)
Andrew Pontzen's Videos
Astrophysicist Andrew Pontzen has made a wonderful 1.5 min video introduction to his work on simulations of galaxies, originally produced for a BBC program (below). You can also download his visualization of Lyman alpha forest line formation.
MIT-style K12 videos
MIT has launched a project where graduate students make 5 min videos explaining science concepts to K12 students using live-action demonstrations or animation. Harvard Astronomy students could make similar brief videos to explain the basic physical concepts underlying their thesis work.
As an example, see the video on Indoor Flying Robots
As a lighter example, see Fast and Slow Changes to Earth's Surface:
Online Chemistry Textbook
MIT grad student Tyler DeWitt has made dozens of Khan-style videos explaining the basics of chemistry, an "online video chemistry textbook". Harvard Astronomy students could make a similar video series focusing on the concepts underlying their thesis work.