Note that many of my house rules on knowledge skills actually became official rules in D&D 3.5.
  1. Knowledge(arcana): In addition to magic per se, gives information about constructs and living supernatural creatures from the material plane (magical beasts, aberations, constructs, dragons)
  2. Knowledge(nature): Gives information about non-magical, unintelligent, creatures native to the area (beasts, animals, oozes, plants).
  3. Knowledge(savage humanoids): Gives information about savage humanoids and their turf, habits, and culture. Doesn't give language.
  4. Knowledge(planes): Gives information about outsiders.
  5. Knowledge(religion): Gives information about undead.
  6. Knowledge(city-state): For each city-state, knowledge about the geography, culture, law, politics, and history of the city-state.
  7. Knowledge(waste region): Knowledge of the geography and inhabitants of the waste region, e.g., Know(Haunted Lands) could be used to find rivers in the Haunted Lands or remember the name and nature of the undead overlord of a certain region of the Haunted Lands.
  8. Knowledge(geography,law, politics, history): covers one aspect of culture of all city-states, as well as waste regions if appropriate. (There aren't many laws in the Great Ooze.)
  9. For each cult except Sophia, there is a Knowledge(cult) skill that gives information and gossip about internal cult matters. This skill is considered class for initiates in the cult. (Know(cult) is a good way for non-knowledge and skill classes to have some useful non-combat abilities, e.g., a fighter or paladin.) Also, it has synergy with other skills and ability checks as follows:
    1. Isthar: Bluff and Intimidate, when the character is name-dropping. Know(politics).
    2. Enkidu: Survival, when actually used to survive in wilderness areas (represents finding hidden shelters and supply dumps)
    3. Ellander: Know(law), Know(history).
    4. Caerfallin: Spellcraft, when counter-spelling; Gather Info (represents confessions made in confidence)
    5. Beryl: Heal, when using herbal remedies; GatherInformation and Know(local) for the doings and attitudes of peasants.
    6. Raq: Know(religion) for undead; Know(planes) for demons and devils; turning undead checks (but doesn't stack with Know(religion) synergy bonus)
    7. Gradulf: Know(Gradulfheim), Know(politics), Appraise (metal and stone)
    8. Durin: Appraise (metal, stone, magic), Crafts(metal, stone, weapons), Know(engineering)
    9. Hillesa: Know(tactics and military); Constitution checks for fatigue from running
    10. Molosh: Appraise(magic), Spellcraft for learning new spells
    11. Hikitami: Craft(all); Know(local) and Gather Info for finding black market services
  10. For Sophia cultists, there are Knowledge skills for each temple, that become class skills when affiliated with the temple.
    1. Rai-Nocturne: Know(politics), +2 to percentile checks for divination magic
    2. Mord-Natava: Heal for midwifing or forensics, Prof(undertaker), Know(religion) for undead; turn undead checks (but does not stack with other synergy bonuses)
    3. Haran-Tempe: Know(engineering) for canals, etc.; Know(nature) for weather prediction, Survival in floods, deserts, or storms
    4. Petra-Aeth: Know(dungeoneering), in natural caverns; Know(geography)
    5. Flora-Herme: Know(nature) for identifying plants and animals, Handle Animal, Prof(farming)
    6. Belic-Serena: Diplomacy, Know(military)
    7. Bella-Male: Sense Motive
    8. Ortho-Eris: Know(politics)
    9. .