The blog Genea-Musings recently published an article linking to a spreadsheet someone had complied containing links to newspaper archives. This spreadsheet has over 13,000 collections, mainly from Genealogy Bank, Newspapers.com, Newspaperarchive.com, Ancestry.com, Old Fulton Post Cards, Google News Archives and Elephind. You can find the spreadsheet at https://drive.google.com/file/d/0B1cdsFRokSx_RnpqUjQwanJvNlk/view?pli=1 however, you must log into Google to see or download it.
The Online Historical Newspapers Website is another place whee you can also find links to all the online historical newspapers.