Kingdom of Loathing Spoilers - Guide covers quests, recipes, trophies, and other in-game information. - http://zerokelvin.org/kol.html
KoL Familiar Tool - Input your familiar's species, and the species and weights of the opponents in the Cake-Shaped Arena, it suggests which battles to choose for greatest experience. - http://www.few.vu.nl/~rminne/kol/kolfamiliars.php
Kingdom of Loathing Bartending Guide - Drink recipes, table of drunkenness and effects, and optimal drinking strategies for gaining adventures, Muscle, Mysticality, or Moxie, with or without Liver of Steel. Available as PDF file or PNG images of each page. - http://www.bellsouthpwp.net/e/p/epeterso2/KOL_Bartending_Guide.html
Kingdom of Loathing: Item Effects - Shows average gains of ingested foods, drinks and items used by a lot of KoL players. - http://www.lysator.liu.se/~jhs/KoL/effects/
Visual KoL - Drink recipes for disco bandits and others, chow mein recipes, uses of scrumptious reagents and dry noodles, and complete Oyster Egg effects and locations. - http://kol.thraeryn.org
Familiar Strengths - Chart with strengths of each familiar and advise on how to do well at the Cake-Shaped Arena in the Nearby Plains. - http://www.the-rye.dreamhosters.com/familiars/
KOL Source - Gameplay hints, including explanations of campground items, list of items at each location, and benefits of the various outfits. - http://www.kolsource.com/
purpleandgrey: Kingdom of Loathing - Tips including recipes, trophies, familiar abilities, and skills available to each class. - http://www.purpleandgrey.com/kol.php
Subjunctive KoL - Exhaustive lists of just about every feature of Kingdom of Loathing, including pants, hats, and weapons sorted by power, adventures possible and items available in each area, effects, recipes, quests, and rewards in Fernswarthy's Basement. - http://www.subjunctive.net/kol/FrontPage.html