I'd like to try the blue Hopi corn,  can get any more native than that.  But haven't found what to get for beans and squash.

http://www.nativetech.org/cornhusk/threesisters.html

http://faq.gardenweb.com/faq/lists/teach/2003045238014436.html

Here's the most info:

http://www.reneesgarden.com/articles/3sisters.html 

And they sell the heirloom seed combo:
http://www.reneesgarden.com/seeds/bonuspacks.html

A living history trio: this handsome bonus packet contains three inner packets of heirloom seeds: multi-colored Earth Tones Dent Corn, Scarlet Runner Beans to twine up the corn stalks and Sugar Pie Pumpkins to cover the ground. 

It doesn't say how many seeds there are, I want to grow at least two circles.

Here's a lot more info:
http://www.kidsgardening.com/growingideas/PROJECTS/MARCH02/mar02-pg1.htm

Last year I thought I had corn growing below the bird feeder until a neighbor clued me in that it as millet.  Amazingly, the rabbits only ate very little of it.