Here are the web pages of related courses with useful notes.
Graph Partitioning and Expanders, by Luca Trevisan
Spectral Graph Theory, by Alexandra Kolla
Spectral Graph Theory and The Laplacian Paradigm, by Gary Miller
Spectral Graph Theory and Algorithmic Applications, by Amin Saberi
Spectral Graph Theory, by Tomas Sauerwald and He Sun
Randomized Algorithms, by Nick Harvey
A course in Spectral Graph Theory, by James Lee
Spectral Algorithms, by Lap Chi Lau