Linear Methods of Applied Mathematics
This is a WWW textbook written by Evans M. Harrell II and James V. Herod, both of Georgia Tech. It is suitable for a first course on partial differential equations, Fourier series and special functions, and integral equations. Students are expected to have completed two years of calculus and an introduction to ordinary differential equations and vector spaces. Topics include Fourier series, Green's functions, and PDEs.

Methods in Mathematical Physics
Covers Complex variables, special functions, second order linear ODEs, asymptotic expansions, Laplace transforms. (One large PS file)

Geometry and Physics
A 33 page lecture from Oxford on the uses of geometry in physics.

Methods of Mathematical Physics I
A set of lecture notes for this one semester course.

Preparation for Gauge Theory
Class lecture notes at a graduate level on the mathematical background needed to understand classical gauge theory.

Spinors in Physics and Geometry
A fourth year math/physics course at UIUC with online lecture notes.

Mathematical Methods in Physics
Covers Conformal Field Theory, Modular Functor, Topological Quantum Field Theory and Frobenius Algebras, Operads, Homotyopy Algebra.