Our Marble tutorials at:

http://techbase.kde.org/Projects/Marble/MarbleCPlusPlus

have lots of chapters (about a dozen) which you can browse through by clicking on the link behind "What's Next".

However currently the sort order is almost more or less random.

• Create a list of all topics (existing ones including the new ones developed during GCI)
• Sort this list so that the topics match this list: http://techbase.kde.org/Projects/Marble#With_C.2B.2B
• Ask a mentor where to put the remaining topics
• Have the new list approved by one mentor
• Now take the new list and adjust the "What's next" entries and "Prerequisites entries to this new order starting from the first chapter (Hello Marble).
• Finally adjust http://techbase.kde.org/Projects/Marble#With_C.2B.2B to the new list as well.