Note that many of my house rules on knowledge
skills actually became official rules in D&D 3.5. 

<OL>
<LI>
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)
</LI>
<LI>

Knowledge(nature): Gives information about non-magical,
unintelligent, creatures native to the area (beasts,
animals, oozes, plants).
</LI>
<LI>

Knowledge(savage humanoids):  Gives information about
savage humanoids and their turf, habits, and culture. 
Doesn't give language.
</LI>
<LI>

Knowledge(planes):  Gives information about outsiders.
</LI>
<LI>

Knowledge(religion):  Gives information about 
undead.  
</LI>
<LI>

Knowledge(city-state): For each city-state, knowledge
about the geography, culture, law, politics, and history of
the city-state.  

</LI>
<LI>
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.  
</LI>
<LI>

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.)
</LI>
<LI>  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:
<OL>
<LI> Isthar:  Bluff and Intimidate, when the character
is name-dropping.  Know(politics). 
</LI>
<LI> Enkidu:  Survival, when actually used to survive
in wilderness areas (represents finding hidden shelters
and supply dumps)
</LI> 
<LI>Ellander:  Know(law), Know(history). </LI> 
<LI>Caerfallin:  Spellcraft, when counter-spelling; Gather Info 
(represents confessions made in confidence)</LI> 
<LI>Beryl:  Heal, when using herbal remedies; GatherInformation
and Know(local) for
the doings and attitudes of peasants.
</LI> 

<LI>Raq:  Know(religion) for undead; Know(planes) for
demons and devils; turning undead checks (but doesn't stack
with Know(religion) synergy bonus) </LI> 
<LI>Gradulf:  Know(Gradulfheim), Know(politics), Appraise (metal and
stone) </LI> 
<LI>Durin:  Appraise (metal, stone, magic), 
Crafts(metal, stone, weapons), Know(engineering)
</LI> 
<LI> Hillesa:  Know(tactics and military); Constitution checks for
fatigue from running </LI>
<LI> Molosh:  Appraise(magic), Spellcraft for learning new spells
</LI>
<LI> Hikitami: Craft(all); Know(local) and Gather Info for finding 
black market services </LI>
</OL>
</LI>
<LI>
For Sophia cultists, there are Knowledge skills for
each temple, that become class skills when affiliated
with the temple.
<OL> 
<LI> Rai-Nocturne: Know(politics), +2 to percentile checks
for divination magic </LI>
<LI> Mord-Natava:  Heal for midwifing or forensics,  Prof(undertaker),
Know(religion) for undead; turn undead checks (but does not stack
with other synergy bonuses) 
</LI>  
<LI> Haran-Tempe:  Know(engineering) for canals, etc.; Know(nature)
for weather prediction,  Survival in floods, deserts, or storms </LI> 
<LI> Petra-Aeth:  Know(dungeoneering), in natural caverns; 
Know(geography) </LI>
<LI> Flora-Herme: Know(nature) for identifying plants and animals,
Handle Animal, Prof(farming) </LI>
<LI> Belic-Serena:  Diplomacy, Know(military)</LI>
<LI> Bella-Male: Sense Motive </LI>
<LI> Ortho-Eris: Know(politics) </LI>.
</OL>