maths.orger.org
by Owen Orger
Level 11 - Undergraduate maths part 5 (Based on the 2 courses in my second year at Cambridge that require levels 11.1-11.3, which are also third year courses, to do fully rigorously)
11.1 - Probability and measure theory
11.2 - Linear analysis
11.3 - Analysis of functions
11.4 - Variational principles
11.5 - Methods