One of my favorite roadmaps of all times was Dwarf Fortress:

http://www.bay12games.com/dwarves/dev.html

It's been greatly simplified since they first started doing it. But it's nice to see a massive project split into arcs, and satisfying to watch things go from white to pink to blue to green. I haven't played the game in years, but I still watch the development.

Initially, a lot of the features came in the forms of stories:

http://www.bay12games.com/dwarves/dev_story.html

As in actual short stories, and how to implement them into game mechanics.

Does anyone else have a favorite roadmap that you read just because they're enjoyable to read?