There is a 32 person #mailart exchange going on at the moment in which 32 people are sending a piece of mailart to everyone else on a mailing list.
The whole thing is being arranged by Art_news
and he's decided to put another one together in July.
That's 30 postcards in a month, starting at the start of July and ending in August.
To see more details check out http://markphilipvenema.wordpress.com/2009/06/10/second-mailart-group/