GameSpot
Review by Desslock, [7.5/10]. "Fails to provide as compelling an experience as Diablo, but does provides a good quantity of new monsters, items, spells, and settings."
Hellfire at DiabloII.net
Large Hellfire resource including strategy, guides, guilds, new items and character classes.
Level 80
Includes details on accessing secret Easter eggs and transferring characters.
PlanetDiablo: Hellfire
Offers information on quests, characters, spells, items, and shrines
The Adrenaline Vault
Reviewed by Jordan Thomas, [4/5]. "Even with the released lack of multiplayer and a couple of irritating elements, this is one fun dungeon crawl."