Since many spells build on prior related knowledge, they generally fall into classical divisions or categories, though some crossover and even redundancy is readily acknowledged. This can be useful for organizing the information.
Truth: eg. Detect Lie, Detect Direction, Translate, Detect Hidden Object
Health: eg. Heal Injury, Cure Poison, Raise Dead
Blessings: eg. Agile, Perceptive, Improved Aim, Favor
Mind: eg. Rally, Detect Motive, Charm, Confuse, Read Mind
Beast: eg. Repel Beast, Tame Beast, Command Beast
Matter: eg. Ion Shield, Convert Element, Dematerialize
Space: eg. Locate, Relocate, Resize
Time: eg. Slow Time, Quicken, Time Travel
Motion: eg. Launch Object, Accelerated Attack, Telekinesis
Portal: eg. Detect Ley Lines, Open Portal, Seal Portal
Force: eg. Alter Mana, Force Field
Heat: eg. Create Heat, Nullify Heat
Vibration: eg. Create Sound, Shake Object, Earthquake
Gravity: eg. Lighten, Burden, Float, Fly
Light: eg. Night Vision, Mage Light, Create Vision
Charge: eg. Charge Object, Lightning
Magnetic: eg. Magnetize Object, Magnetic Shield
Fire: eg. Ignite, Fireball, Fireproof
Fluid: eg. Wind, Pressurize, Storm, Tornado
The following are simply handy reference lists for cross-reference:
Attack: a list of spells favored for combat attacks
Defense: a list of spells favored for combat defense
Thievery: a list of handy spells for thieves