Rope Sling

My sling was made using about 7 feet and 6 inches of nylon cord. Easy to do ,but does take some concentration. I found this amazing tutorial on YouTube-http://www.youtube.com/watch?v=APExNLO1oHY. I had to watch it a couple of times to get it but i am very new to knots so a veteran would probably find it quiet easy. 
  Ive only just started to really take interest in knots and i have found they really are cool. The person who made that video's channel is really useful and defiantly recommended. Tying It All Together. I am aiming to try and find a really good comprehensive guide to knots so any recommendations would be helpful, thanks.