the copy-left ATC edition is kind of a follow up to the trading day - it's a very practical way to trade cards internationally (when you can't meet other artists personally).
it basically works pretty much like the single card trade: you send in an edition of 20 cards and you will get back a set of cards by 15 different artists. it is published about once a week. it is an ongoing project and there is no theme.

send 20 ATCs (20 different ones or 20 times the same)
size 2 ½ x 3 ½ inches (64 mm x 89 mm)
sign, number and date on the back of the card
no theme, all techniques
no deadline
you will get a set back

send it to:
COPY-LEFT
c/o INK.art & text
dufourstrasse 132
ch-8008 zürich
switzerland