Bountiful Gardens, a company created by Ecology Action, is devoted to sustainable growing. They help small farmers and individuals grow the best quality produce, as well as crops for compost, income generation, and household needs. Their information is based on many decades of test gardens from around the world. They are devoted to their cause.
Seeds, tools, and gardening information can be found at: http://www.bountifulgardens.org
They have also authored many pamphlets, and a book: How to Grow More Vegetables, which I highly recommend.
Bountiful Gardens & Ecology Action also put on an intensive sustainable gardening class in Willits, CA. Well-worth the travel and expense.