Refraction:

• A history of Fermat's work on refraction.
• Refraction simulation

Predecessors to the Calculus:

• Method of Maxima and Minima
  • Letter from Fermat to Brûlart, March 31, 1643
• Method of Quadrature

Arithmetic

• Observations on Diophantus
  • First Challenge to Mathematicians, Jan 1657
  • Second Challenge to Mathematicians, Feb 1657
  • Fermat to Frenicle February 1657 − arithmetic challenge
  • Fermat to Carcavi October 1659 (On his method of Infinite Descent)

Probability

• Fermat to Pascal 1654
• Pascal to Fermat July 29, 1654
• Pascal to Fermat August 24, 1654
• Fermat to Pascal August 29, 1654
• Fermat to Pascal September 25, 1654
• Pascal to Fermat October 27, 1654

Other Works

• Introduction to Surface Loci
• On the Solution of Problems of Geometry, Using the Simplest Curves
• Geometric Fragments