``Artin groups and polytopes,'' Equipe Algebre-Géométrie-Topologie, Université de Bourgogne, Dijon, France, June 2005
``Constructing non-positively curved spaces and groups'', California Polytechnic State University, San Luis Obispo, May 2004
``Algorithmic aspects of curvature'', University of California, Santa Barbara, March 2002
``Calculating curvatures of concrete complexes'', Unversity of Texas, December 2000
``Calculating curvatures of concrete complexes'', Karcher Colloquium, University of Oklahoma, October 2000
``Calculating curvatures of concrete complexes'', Vanderbilt University, September 2000
``General versions of small cancellation theory'', Texas A&M Univerisity, January 1999
``Constructing compact cores in negatively-curved 3-manifolds'', University of California, Davis, January 1999
``Constructing compact cores in negatively-curved 3-manifolds'', State University of New York, Binghamton, February 1999
``Constructing compact cores in negatively-curved 3-manifolds'', Rice University, December 1998
``From differential geometry to word hyperbolic groups: a combinatorial approach to an analytic idea,'' Graduate Student Colloquium, Texas A & M University, October 1998
``Roots, ratios, and Ramanujan,'' Lafayette College, Easton, Penn., October 1998
``From differential geometry to word hyperbolic groups: a combinatorial approach to an analytic idea,'' Special Colloquium, University of Kentucky, Lexington, Kentucky, February 1998