Open Access: To What?
ESSENTIAL:  

to all 2.5 million annual research articles

published in all 24,000 peer-reviewed  journals (or conferences) in all scholarly and scientific disciplines, worldwide


OPTIONAL:
(because these are not all author give-aways, written only for usage and impact)
1. Books
2. Textbooks
3. Magazine articles
4. Newspaper articles
5. Music
6. Video
7. Software
8. “Knowledge”

(or because author’s choice to self-archive can only be encouraged, not required in all cases):
9. Data
10. Unrefereed Preprints