The individual blog options for making a post seem to be:
Everyone (Public)
Access List
Private (Just You)
Custom Filter

The community options for making a post:
Everyone (Public)
Members
Administrators

Posting access to a community may be:
Everyone (even nonmembers)
All members
Select members

Which is odd, because I know I've seen references to settings like "registered Dreamwidth members" or "logged in Dreamwidth members" but I can't find them right now. :/