Step One: Understanding the current site building blocks
Here I mapped out the audience, potential actions and existing content.
Step Two: Mapping out the proposed structure makes sure I have accounted for all the pieces.
Step Three: Trying a few potential organizational schemes helps to break out of the existing structure to see how else we might approach the content.
This first one is by content type, which is useful for users who know specifically that the information they are looking for comes in a specific format. In Google Analytics I saw that publications were very popular - it seems like OSA is a destination for reports on a number of topics. To support that behavior I used this organization for part of the nav bar.
Next I binned the content by its location on a timeline. This method helps delineate how content shifts in relevance for the user and how it is created by OSA. It was useful for coming up with the newsletter/blog/nav bar process.
Next I split up the content by what action might be taken with it. I decided to use different verbs than you are currently using so that we could think without any existing boxes. Here's how I would 'define' the verbs and allocate their audience:
Experiment (researchers): discovering new ways to practice various activities with organic seeds
Practice (farmers & gardeners): using proven and documented techniques to achieve specific outcomes with organic seeds
Understand (advocates, everyone): learning the general issues, definitions and news surrounding organic seeds.
Connect (everyone): getting in touch or involved with an organization or person.
Step Four: Putting the parts together
I realized there were some patterns in the separation of content by timeframe and by action, so I put them into a matrix. In red you can see the rough mapping to the existing categories along the top and to the timeframes along the side.
We talked a bit about the difference between the newsletter and the blog, I thought a simple way to clearly delineate them was by timing - the newsletter 'announces' upcoming items, the blog 'archives' what is current and anything you want to live on forever goes into the nav bar. This is rather theoretical, so we can talk more about this and what it would mean in reality!
Step Five: Potential layout
Here I made some preliminary decisions on how to group the content. For continuity in the process, I stuck with my action types, which I don't expect you to do! There are three sections I would suggest using the toolkit feature to clearly expose content sub-categories. I also listed content types under 'Practice' but I would imagine there to be a 'Practice' toolkit-style page where you can also look at all the content by subject area. 'Understand' may use the toolkit feature for when a user clicks on the main nav instead of an item from the list. I just realized I didn't draw in the list items for Scientific Literature or OSA projects, but those would both live in the 'Experiment' group. I separated 'Connect' from the last step into the Seed Network/Community list you provided and put the others (Contact, Donate, Partners) as static pages.