I have made and will maintain an up-to-date Urbit Hoon reference card. (I am segregating my course-related work very carefully from my Urbit-hobbyist work—although I will use this should my grad course be approved by the dept I am putting it forward as a public resource.)
You can see the current version here: https://github.com/natareo/hooncard/blob/master/hooncard.pdf
I put 1 star, but, whatever, I don't really think this is worth a whole star—I was encouraged to put this up as a proposal, which has the added benefit of making Tlon aware that this now exists. But if not, a Nock shirt or the like would be nice.