These are quick reference cards that I've collected for my own use whenever I needed one but they are also available here so hopefully you'll find them useful too. Some are really great but some are just the best I could find for now & I'll replace them when I can.
All files are in PDF format unless otherwise stated.
Last update: May, 2017: Added TypeScript, Kotlin, React, Angular and Android layouts.
Many of the cards are from this site which has more cards not listed here. Another good source (not as many cards though) is this site.