Below are materials for various classes, seminars, and the like I've run in the past.

Proof-based linear algebra
Handouts from Math 115 at UCLA and Math 242 at CMU

Descriptive set theory
Outline, problems, and scant notes from a seminar

Various REUs and DRPs
Collected from various research and reading projects with undergraduates

Qual Solutions
Salvaged from the now inoperable UCLA grad wiki