These Web-accessible expositions deal with the topics of the Workshop on Semiclassical Approximation and Vacuum Energy. (They should not be thought of as "prerequisites". The program included a number of introductory lectures.)

• A. Uribe, Trace formulae (in First Summer School in Analysis and Mathematical Physics: Quantization, the Segal-Bargmann Transform and Semiclassical Analysis (Contemp. Math. 260), ed. by S. Perez-Esteva and C. Villegas-Blas, American Mathematical Society, Providence, 2000, pp. 61-90).
• D. Cohen, H. Primack, and U. Smilansky, Quantal-classical duality and the semiclassical trace formula (Annals of Physics 264 (1998), 108-170).
• S. Zelditch, Survey of the inverse spectral problem (to appear in the JDG Surveys).
• J. Bolte, Semiclassical trace formulae and eigenvalue statistics in quantum chaos (lectures at 3rd International Summer School/Conference Let's Face Chaos through Nonlinear Dynamics, Naribor, Slovenia, 1996).
• J. Marklof, Selberg's trace formula: An introduction (lectures at International School Quantum Chaos on Hyperbolic Manifolds, Gunzburg, Germany, 2003).
• K. A. Milton, The Casimir effect: Recent controversies and progress (Journal of Physics A 37 (2004), R209-R277).
• S. A. Fulling, Global and local vacuum energy and closed orbit theory (in Quantum Field Theory Under the Influence of External Conditions, ed. by K. A. Milton, Rinton, Princeton, 2004, pp. 166--174).
• R. L. Jaffe and A. Scardicchio, Casimir effects: An optical approach. I (Nuclear Physics B 704 (2005), 552-582).
• S. De Bièvre, Quantum chaos: A brief first visit (in Second Summer School in Analysis and Mathematical Physics: Topics in Analysis: Harmonic, Complex, Nonlinear and Quantization (Contemp. Math. 289), ed. by S. Perez-Esteva and C. Villegas-Blas, American Mathematical Society, Providence, 2001, pp. 161-218).
• Some references on quantum graphs