Massimo Vignelli shares an amazing wealth of knowledge with us, the graphic design & typographic principles he's developed throughout his career in "The Vignelli Canon".
In several teaching situations I remarked the lack of some basic typographic principles in young designers. I thought that it might be useful to pass some of my professional knowledge around, with the hope of improving their design skills. Creativity needs the support of knowledge to be able to perform at its best.
It's an essential resource for designers of all disciplines and best of all it's available to download in PDF format for free--nice one.