nLab
mathematics

Structural Foundations with annotated toc of 3 great books with numerous links to related nlab content:

• Categories and Sheaves

• Sheaves in Geometry and Logic

• Higher Topos Theory

Topology and Geometry

• geometry (general list), topology (general list)

• general topology

• algebraic topology

• homotopy theory

• rational homotopy theory

• differential geometry

• differential topology

• algebraic geometry

• noncommutative algebraic geometry

• noncommutative geometry (general flavour)

• higher geometry

• Lie theory

Algebra:

• universal algebra

• higher algebra

• group theory (including generalizations)

• representation theory

• algebraic approaches to differential calculus

• homological algebra

• gebras (co(al)gebras, bi/Hopf-algebr-as/oids…)

mathematical analysis

• nonstandard analysis, functional analysis, operator algebras

discrete mathematics:

• set theory, category theory

• graph, directed graph, order, poset, filter…