CFL official website There isn’t much history here, but it does have up-to-date information about the teams. And the link at the bottom of the page, Grey Cup Central has a lot of information about specific Grey Cup games.
Canadian Football Hall Of Fame Some history about the CFL, more history about the Hall of Fame and the Grey Cup.
Canadian Encyclopedia A very good write up on the history of professional football in Canada (CFL)
Canadian Encyclopedia Grey Cup
Wikipedia … this may be the most comprehensive website for information
Wikipedia Canadian Football
Wikipedia CFL >>> Very good information here.