This may be helpful: catholicculture.org/library/view.cfm?recnum=3635
Its purpose is a long-term plan of self-improvement (concentrating on one virtue per month), but it does give a lot of examples of mortal and venial sins.
I was really surprised at a few of the sins that are listed as mortal (has our society changed that much since it was written in 1942?). In any case, it’s good to have a trustworthy priest-confessor, and if you are unsure as to whether something is mortal or venial, ask him. And certainly confess it if you think it might be mortal.
(Note: lists like this should probably be avoided by persons suffering from scrupulosity.)