This utility is offered in the spirit of a digital — a tribute to sociologist (1927–1998). (Luhmann built up a zettelkasten of some 90,000 index cards for his research, and credited it for enabling his extraordinarily prolific writing (including over 70 books and 400 scholarly articles)).
His basic purpose was to link these cards in a meaningful way so that he could use them to generate new ideas, papers and projects. The advent of powerful, digital databases make this job much easier.
I have taken one step further and designed cards that are graphic-rich and provide a quick synopsis of the idea behind an article or post. Links are provided to the original source for in-depth reading.