I was introduced to Artist Trading Cards in College by my drawing instructor Don Mabie. Artist Trading Cards are a new spin on the ever popular sport trading card. Because this kind of artmaking lacks elitism, it is geared towards anyone to participate.
The New Gallery in Calgary is involved in monthly trading sessions, where everyone is invited to look and to trade. This site also gives the history of ATC's and other great links.
Take a look at other artists' Trading Cards.
Or meet up with people in your area and start your own trading sessions.
Remember there are no rules, except the size of the card!!
The Envelope is the Museum.... Mail Art is another form of sharing art. It's a grand daddy to Artist Trading Cards, and has a more elitist history, including many famous artists such as Yoko Ono.
