I wrote the following pieces of code (mostly for my own amusement):

• continued_fractions.c: this C program computes the positive and negative continued fraction expansion of a rational number;
• correction_terms.rb: this Ruby program computes the correction terms of lens spaces.
• torus_knots.c: this C program computes some data for (positive) torus knots; among them, the coefficients of the Alexander polynomial, their torsions, and correction terms of their (positive) surgeries.