Instructables
550 cord or simply para-cord, refers to a specific class of parachute cord also known as type III cord and derives it's name from being rated to have a minimum breaking strength of 550 lbs. Mass production and the near infinite usefulness of this wonderful stuff has brought it into the lives of all of us. We couldn't let the paratroopers have all the fun! 

This handy guide will give you a hint at some of the things you can do with 550 cord.