Pokémon Gold and Silver

Articuno3000's PKMN
Contains tips and GameShark codes.
http://www.geocities.com/oakely_ray_aaron/Articuno3000_Pokemon_Page.html

Cheats Codes Guides: Pokemon Gold
Cheats, tips, and Pokemon locations.
http://www.cheatscodesguides.com/game-boy-color-cheats/pokemon-gold/

eLook
Quick summary of cheats and codes
http://www.elook.org/games/cheats/gbc/618.shtml

Games++
Offers cheats and hints.
http://www.gamespp.com/gameboy/hintscheatcodes/PokemonGold.html

IGN - Pocket Pikachu Color
Virtual pet stand alone handheld game. Works with Gold and Silver. <small>(October 15, 1999)</small>
http://gameboy.ign.com/articles/071/071278p1.html