The site is packed with really good information: videos, bulletins, fact sheets on research, and newsletters. Many of these items are specific to a region in the U.S. (Western, Southern, North Central, Northeast).
They also offer free online courses/curricula through their Learning Center. Just click on this link to view all the offerings - you will need to register to start. Some of the courses are designed more the extension agents, but they are still free to anyone. Not too many yet, but a great resource for free education!
If you are interested in performing research on Sustainable Agriculture, this site is your source for grants to fund your project.
If you have a chance, I highly recommend that you take the time to browse this site.