From time to time a mathematician is invited to give a talk that is specifically for undergraduates. Recent speakers and their topics are listed below.
David Morrison Stalking the Shape of the Universe
(Duke)
J. H. Conway Some Tricks with String
(Princeton)
Persi Diaconis The Mathematics of Shuffling Cards
(MIT)
Joseph Gallian Touring the Torus
(U. Michigan)
Robert Devaney The Mathematics behind the Mandelbrot Set
(Boston)
Donald Knuth Leaper Graphs
(Stanford)
Colin Adams Real Estate in Hyperbolic Space
(Williams)
Jeffrey Weeks Visualizing Four Dimensions
(Minnesota)
Lloyd N. Trefethen Computational Mathematics in the 1990's
(Cornell)
Underwood Dudley Formulas for Primes
(DePauw)