Permaculture Activist has been running a permaculture periodical for nearly a quarter century now. The website also has some articles available online, and links to more articles and sites.
The Holistic Agriculture Library contains public books and articles (hard to find and out-of-print) on soil health.
e360 is published by Yale’s School of Forestry & Environmental Studies.
The tiny (new?) site at Soil Carbon doesn’t offer much information, but it is one of the only groups dedicated to increasing awareness about the connection between carbon sequestration and healthy soil.
Sustainable Agriculture Research and Education (SARE) provides grants and information regardingn sustainable agriculture.
International Center for Agricultural Research in the Dry Areas. I haven’t looked through this thoroughly, but it seems to have a wealth of information.
[...] Sustainable Agriculture [...]