So there is Spontaneous, Vancian, and Mana/Focus Points.
But what other kinds of casting is there?
(*Ignoring balance for the moment.)
PolyArcana "You can cast any spell, but once you do, you cannot cast that same spell again until you cast 10 different spells."
Spell Chain: "Choose the next 10 spells you will cast, and the order you will cast them."
Spell Roulette "Choose 10 spells. Each time you cast, roll a d12 to determine which spell you cast. If you roll an 11, you don't cast any spell. If you roll a 12, you can choose. You can choose your target after you roll."
Spell Deck "Make a deck of cards with your spells and shuffle them. Then draw 5 cards. You can cast any of those 5 spells, discarding it when you do, and drawing a new card. You can spend 10 minutes to refocus, discarding all your cards, reshuffle your deck, and draw 5 new cards."
Inconsistent Power. "Roll a die. You can cast a spell of that level."
Spell Slot Bingo. Not sure how this would work, but it sounds fun.
Any other ideas?
So there is Spontaneous, Vancian, and Mana/Focus Points.
But what other kinds of casting is there?
(*Ignoring balance for the moment.)PolyArcana "You can cast any spell, but once you do, you cannot cast that same spell again until you cast 10 different spells."
Spell Chain: "Choose the next 10 spells you will cast, and the order you will cast them."
Spell Roulette "Choose 10 spells. Each time you cast, roll a d12 to determine which spell you cast. If you roll an 11, you don't cast any spell. If you roll a 12, you can choose. You can choose your target after you roll."
Spell Deck "Make a deck of cards with your spells and shuffle them. Then draw 5 cards. You can cast any of those 5 spells, discarding it when you do, and drawing a new card. You can spend 10 minutes to refocus, discarding all your cards, reshuffle your deck, and draw 5 new cards."
Inconsistent Power. "Roll a die. You can cast a spell of that level."
Spell Slot Bingo. Not sure how this would work, but it sounds fun.
Any other ideas?
The alchemist is itself a kind of modified mana caster: all their spells (formula) are essentially all max level and they can "commit" one mana each morning to cast a given spell more or they can "hold" their mana to cast a spell more times later.
There are also "X per day" systems (such as Shadow of the Demon Lord) where you know a certain selection of spells but you can cast lower level spells more times than higher level spells (and the exact number of each you can cast scales on your power level/caster level).
There are "spells as consumables" where spells are limited by the costs of their components alone.
You may want to look at the tome of magic some of the Frank Brunner 3.5 books as well:
Tome of Magic (3 different magic systems here: skill check based, X/Day based, and whatever Vestiges are)
Magic of Incarnum (which foils attempts at quick summary)
Tome of Battle (Which also has like 3 totally different magic economies)
Speaking of Frank Brunner magic systems, you could also consider how Spellbound Kingdoms does combat styles and magic styles (a sort of flow chart system)