I've come to this style from one of my favorite artist/designer/illustrators Von Glitschka.
It is rather self-explanatory: create an illy using one line or the appearance of a single, continuous line for the gist of the illustration. It's a fun way to simplify down to the contours and with the impression of values through mapped shadows. From youth, I've been a big fan of the Etch a sketch, and most of my normal drawings and illustrations have not gotten past the "line art" stage to enter full completion. So here we have a style that actually rewards simplicity, allowing the same line that gives contour to flow through negative space with varying width to provide form as well. It's perfect for the lazy individual such as myself. :P
Anyway, are there any here familiar with the style? Care to upload what you've done? I'd love to dabble with this approach even more, but here are a few, very basic ones of my own:
For Von Glitschka's 21 Day Draw challenge, where I was first acquainted with continuous line:
And my avatar, a self portrait: