The sources for the following reference cards is on Github.
Periodic Table of Elements
Last updated: 2018
Contains atomic weight, mass number for most abundand isotope, atomic number, full electron configuration, valence electrons, and nuclear spin of most abundant isotope with I≠0.
Modern Fortran Reference Card
Vim Reference Card
Last updated: 2010
Contents: Movements; Insertion & Replace; Deletion; Insert Mode; Search & Substitution; Standard Mode Formatting/Filtering; Visual Mode; Undoing; Repeating & Registers; Copying; Patterns; Spell Checking; Marks, Motions and Tags; Multiple Files / Buffers; Scrolling & Multi-Windowing; Misc Ex Commands; Ex Ranges; Completion; Folding, Compiling, Miscellaneous.
Python 2.5 Reference Card
Perl Reference Card
The following reference cards are less polished than the above: