The Diablo 2 Wiki
The Diablo 2 Wiki archive is available for anyone looking for information on Diablo 2. All information here is pre-D2R but contains a lot of useful information that is still relevant. Updated sections for new D2R features can be found on the PureDiablo Diablo 2 section

Category:D1 Monsters

Category page

This category lists all of the monsters in Diablo I and Hellfire. The superunique monster types are listed on the pages with the regular type of that monster.