Blind drawings can be really interesting, especially if you're drawing detailed subject matter such as faces. It gives an effortless abstract result.
February James - Blind Contour Line Drawing
Continuos Line & Blind Drawings
blind contour drawing (also called pure contour drawing) definition and instructions
BLIND CONTOUR drawing three-quarter view self-portrait by seeks posted on http://theseekspeak.blogspot.com/2005/08/blind-contour-friday-03.html
50 Layered Blind Contour Drawings by Tribastone, via Flickr
Today in Art- 8 exercises every artist should practice