I found a list of seed companies that either buy seed from Monsanto or are owned by them. So these are labels/companies to AVOID.

For information on the seed monopoly/concentration problem, here's a good albeit somewhat dated paper outlining the companies involved: http://www.non-gm-farmers.com/news_print.asp?ID=2549

(This list has been compiled by some diligent mothering gardeners. If you have any corrections or additions post them here.)

* Territorial Seeds
* Totally Tomato
* Vermont Bean Seed Co.
* Burpee
* Cook's Garden
* Johnny's Seeds
* Earl May Seed
* Gardens Alive
* Lindenberg Seeds
* Mountain Valley Seed
* Park Seed
* T&T Seeds
* Tomato Growers Supply
* Willhite Seed Co.
* Nichol’s
* Rupp
* Osborne
* Snow
* Stokes
* Jungs
* R.H. Shumway
* The Vermont Bean Seed Company
* Seeds for the World
* Seymour's Selected Seeds
* HPS
* Roots and Rhizomes
* McClure and Zimmerman Quality Bulb Brokers
* Spring Hill Nurseries
* Breck's Bulbs
* Audubon Workshop
* Flower of the Month Club
* Wayside Gardens
* Park Bulbs
* Park's Countryside Garden