The devoted author of Mac 68K Games is, like myself, not afraid to post the unconventional.
UTexas Mac Archive, at my home university, contains only a few choice games, but the list has remained stagnant for at least 5 years now.
Dr. Shareware is a more encompassing catalog of games and other software.
Happy Puppy is a congregating point for commercial demos in addition to shareware games.
Transfix Games rates all games on file and provides other resources such as cheats and news.
Ambrosia MacFiles archives both new demos and old demos which I don't have the time to download on my 14.4K modem with the sucky UT server cutting off as much as it does.