Norm: The Things
The project of Zurich-based design firm Norm: The Things is a book outlining the conceptual framework of their practice by breaking down shapes and fonts into their essential elements. Widely known for their typefaces (they recently designed one for the Swiss Watchmaker Omega), they also won the competition to design a new series of Swiss bills in 2005. The Thing's experimental graphics and text may be a little baffling to those (like me) who are unfamiliar with their theories, but the 2003 book is a great source for any font nerd or for those curious about the relationship between words and images.
More to the point is their Sign-generator, an online collaboration with fellow Swiss designer Jürg Lehni (known for his Mechanical Graffiti invention) that shows users all the available constructions that can be made from a set of lines defined by the user, which you can then print and export.