Lecture notes
A-infinity algebras and type-D structures (WIP)
Commutative Algebra
Invariants of low dimensional manifolds
Geometry of rings and schemes (WIP)
Low dimensional manifolds
Riemannian geometry
Spin and spinc structures
Yang-Mills theory
More books and lecture notes
Allen Hatcher
's page, with his excellent book on algebraic topology
There is always sci-hub and libgen of course