Structure, Look and Feel
Great idea for a project. Thought I'd leave some suggestions planning your resource, including the need for a consistent look and feel,
There was some work awhile back to encourage the creation of plans for learning design and content design. I implemented the concept when I began work on an OpenOffice Calc tutorial; see the box at the bottom of the page, which includes links to learning design and content design subpages. After having thought through many of the aspects of what I wanted to created, the actual creation of the content, I believe, has been much more straightforward and I can leave and come back to the effort knowing I have a built-in refresher.
As to your specific desire to have a consistent look to the pages, my suggestion is to create a style guide for your project. My Calc 3 tutorial content design page includes a link to a style guide useful for a software-related resource. Also there are a number of WE-wide style proposals currently under discussion. You might find a few of these useful for your purposes.
Rob's suggestion to create a navigator (his reference to tutorial 11) is also a key feature in content design.
Definitely design is a key aspect to creating usable content.