Ultima 8, more variety than you can shake a stick at, all sort of nicely thought out, none of them overly weak or powerful, all handy in certain situations, and every school of magic has its distinct feel.
Necromancy:
You research how to cast spells in-game by reading books or speaking to old necromancers. Once you know the necessary ingredients, you gather or buy them, place them in a bag, cast an incantation and then receive a token that you can use to cast the spell at will. The token will disappear after a spell is cast, requiring you to prepare spells ahead of time, or carry all sorts of reagents around.
Thaumaturgy:
You purchase mystical spellbooks outlining the incantation and the reagents for the spell you need, gather them, charge up the book with the reagents, and then use the book to invoke the spell. Once the spell is cast the book must be recharged. Only once charge can be held at once.
Theurgy:
You shape symbols for your spell, one symbol for each spell, from silver you mine. Then you bless the symbols. Now each symbol can cast a spell as often as you want, provided you have enough energy to do so.
Sorcery:
In-game, in a book, you research how to use a pentacle: you learn which part of the pentagrammon has which name, and for every spell, you learn, still in-game, what reagents to place at what parts of the pentragram, along with where to place candles of ash or blood, depending on the spell. Then you put a magic focus into the centre, light the candles, cast the spell and charge up the focus with a certain amount of spell charges. The higher quality the focus used, the more often it will be able to cast a spell, in exchange for spell points. Once it is exhausted you must recharge new foci.
Necromancy deals with Earth and Death, Thaumaturgy with the Astral sphere, Theurgy with Air and Life and Sorcery with Chaos and Fire, each school having a good amount of unique spells.
This system required you to actually learn things in-game, memorize things like a student (Where does the red candle go again to prepare a Conflagration spell? Did I forget to bring Sulphurous Ash?) and reward you with a sense of accomplishment for becoming proficient in all schools.