I'm going to make some, and I thoroughly encourage others to do so as well. I have some blank postcard paper, but I'm not entirely sure that the paper is going to be sufficient for that. So, I may end up making some that same size out of thicker, more absorbent paper. We shall see on that front.
However, just an added note about mail art, in general....I enjoy the idea of it, the fact that it inherently travels. It has some work to do, and withstand weather and wrinkles and still look good. That's the real challenge I think, to make the pieces look cool after they have taken a beating.
I'm still thinking it all out, but I have decided that for my thank you 'letters' to my references for grad school, that I would make something art-related, something that they could keep or display, if they so chose. Instead of a card with a small painting inside, I thought, 'Why not make the card the art, why not make it a postcard?' If it's cool enough, I think they will work. If not, I'll make something else, like a home-made card and envelope. Which, I have done countless times, but is not thrilling me as much, at this point.
I'll keep updating...