If you're specifically talking about working with text documents, that section of the OO.org Dev Guide really is the way to go:
http://wiki.services.openoffice.org/wiki/Documentation/DevGuide/Text/Working_with_Text_Documents
Note that the document navigation is on the right side, and kind of small. There's similar entry points for Spreadsheets:
http://wiki.services.openoffice.org/wiki/Documentation/DevGuide/Spreadsheets/Working_With_Spreadsheet_Documents
And for drawing documents:
http://wiki.services.openoffice.org/wiki/Documentation/DevGuide/Drawings/Working_with_Drawing_Documents
I think this is the kind of general "cheatsheet" reference you're looking for and I don't think there's any better source for it.