Actually I think we should have 5-6 ways of browsing learning resources as sub categories directly under "Contents" (without the "Open education resources" category. I don't think we should settle on whether to call them learning resources or OER, yet. I think both options are on the table. (The issue being that everything in WE is OER.)
I'd also like to suggest that we don't need to settle on one particular word to describe the class. My suggestion is to list a few of the main words that describe a broad class (e.g., I think we should use both the words "topics" and "subjects" to create a category that includes learning about topics that might not be considered subjects in school).
Jesse, you are right about needing to include age, however, I'd like to combine "age" with "level" and "grade" (I'm now considering certificates in a separate category) to create a category that includes resources broken out according to growth & development and/or experience (I think these two factors are very tied together). I'm not convinced that "age" will serve as a common classifying factor around the world. And besides, individual variation results in 9 year olds studying Feynman's lectures and adults learning how to read. Maybe it's better to leave it up to the wikieducators to say to whom their resource is targeted (in whatever metric works for them). Categorise into a broad category. And then later, once we see what's included, reassess.
I'm getting close to a proposal (at least for this top part). I'll see if I can get it together in the next few days. I'll add it to the main page.
In order for the 5-6 browsing methods to work ideally, every resource would need to be available to every category redundancy (the different categories that mean the same thing). How would we guarantee that?
I'm not sure what you mean, although I agree that forcing a redundancy will quickly undermine any proposed structure. I'm not proposing separate categories that mean the same thing. It's more about how to name a category so it can encompass a broad range of sub-categories. An example is Category:Schools, colleges, institutions or Category:Subjects and topics.
I've made a first proposal for these top categories at Workgroup:Categories/Proposed_map. Maybe you could provide an example of the redundancy using one of the elements in this proposal.