> 50%: The (well-written) syllabi. They point out which resources (books, blogs, websites, etc) are worth your time, if you have an interest in the subject. The best ones are filled with opinions, and "optional resources if you want to dive deeper into X". Even the lazily-constructed ones are a great foundation if you have no idea about how to begin learning X.
Do you have any pointers to online examples of syllabi you found useful? My syllabi are always to the point and focussed on the structure of the class; it's never occurred to me that someone might want to use them as a roadmap for independent learning, and I'd be interested in facilitating that.