The SPARC site has a good discussion of Open Access at the link above.
The SPARC site also has a good discussion of Open Data.
Lists of Repositories
Registry of Open Access Repositories International list of online repositories of scholarly information.
The primary source researchers should use for identifying quality open access journals is the Directory of Open Access Journals: DOAJ.
However, if a journal of interest is not listed in the DOAJ, you may wish to consult the Scholarly Open Access site to determine if the journal would still of interest to you.
Using both of these databases together will help the researcher identify quality journals and avoid other journals.
SHERPA/RoMEO explains publisher copyright policies and what you need to do to keep your copyright so you can deposit a copy of your paper in AUrora.