Blizzhackers
Includes hints, tips, and a community forum for those who hack the game.
CheatingPlanet: Diablo II Cheats
Offers some tips and Horadric Cube recipes.
Diablo 2
Hackers, trainers, tips, cheats, and general information.
Diablo II ProTip Guide
Tips including how to use the Horadric Cube, questing tactics, and gameplay advice.
Diablo II Tomb of Knowledge
Horadric cube recipes, gems, skills, items, and quest walkthroughs.
GameFAQs: Diablo II
A large selection of walkthroughs and character guides.
GameSpot
Guides for character classes, and walkthrough.
Lightreaver's Diablo II Site
Provides guides on the various characters in the game.
Miamira
Links, downloadable cheat files and message boards.
NeoSeeker: Diablo II
Walkthroughs, reviews, and message board.
UHS Diablo II Hints
Shows hints gradually so you can finish the game on your own.
Ultimate Diablo Item Editor II
A character and item editor.
VenomousVixen's Complete Sorceress Guide
A comprehensive guide including FAQ, character development, combat, items, and skills.