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In reading the above comments and doing some more thinking, I see three primary uses cases for Netduino collaboration.

1) The newbie user that is just getting started.
They just need tutorials, similar to those on the main Netduino page. I found those really helpful in getting started. I just think we need to continue to build on that library. I know those take more time to put together than it looks.
2) The inexperienced user who has a couple tutorial style projects under his/her belt and wants to add widgets (sensors/motors/whatever) to his board.
I think this user is looking for a list of widgets of they type they are looking for that include links to suppliers, pinout diagrams or wiring schematics that are specific to the Netduino, and helper/driver classes to get their development started. These users are also going to be interested in the project showcases as it inspires them to do more with the toys in front of them.
3) The experienced user is looking for ways to make their development easier and looking for answers on advanced topics like how to guides on writing native drivers, and debugging via RS232.
These users can deal with a little less structure to their content. Tagging articles is probably going to enable the necessary search requirements. These users are also probably the ones that are writing a lot of the content for users 1 and 2.

So looking at those user types I would suggest the following:
Wiki:
Product (Widget) pages
Contains a page for each product that are tagged or otherwise organized by type of product (LCD, stepper, temperature, etc). Each product page has its wiring schematic, a list of suppliers, and link to the helper classes in source control.
Project Showcase
Contains pages for people to share the projects that they have completed. These pages preferable have links to product pages, source control as well. These pages should also have some high level organization such as tags or sub-forums (Robotics, home automation, etc).

Source Control:
User Helper Classes
This should be a code repository (SVN or other) of helper classes and sample usage of the classes. Ideally they also have comments that link them back to some sample product pages. This allows people to search the code repository and get back to the wiki for more info.
Official Community Helper Classes
The difference with these classes is that some "panel" of advanced users considers these the best of the helper classes. My hope would be that the Secret Labs team would be able to take on supporting these and using them as test cases for new firmware versions. But I know that add a lot of support time to the dev/test teams at Secret Labs.
Project Showcase
A place for people to store their project code.

I am just starting to move from user 1 to user 2. I have no idea what user 3 needs. But this is my guess. Hope this helps.