SP Spellcasting (3.5e Variant Rule)
From D&D Wiki
SP Spellcasting is determining how many spells/special techniques a character can cast through assigning each spell and special techniques with a SP(Stamina Point) cost and giving a character a preset total of SP.
Determining a Character's SP and SP Cost
At the first of a class that uses spells/special techniques a player acquires he is considered to have the maximum value of his hit die+his Constitution Modifier. The spells/special techniques used by the character should cost 2 SP×its spell level(even if its not a spell). Thus, the higher the level of spell/special technique, the more it will cost. When a character's SP is 0, he can no longer cast spells/use special techniques (any spell/special technique that costs more SP than the character has cannot be used.)
Replenishing lost SP is done through rest, replenishing 12.5% of his total SP/hour if sleeping or 10%/hour if awake, thus requiring 8–9 hours of rest to replenish a character's SP to his max. SP may also be replenished through consuming certain items like "Ether" or "Energy Drink".
SP maybe also be spent by strenuous activity like running, swimming, climbing. When performing strenuous activity, a character loses 1d2 SP for every minute that the activity is performed. A character may still perform strenuous activity with 0 remaining SP, but they take a -2 exhaustion penalty on any rolls involving the activity and moves at half his base land, swim/fly speed.
Limiting the Use of SP
If a class is intended to be able to cast very spells per day, then reduce the total SP a character begins with by half. In the other case, where the amount of SP is not enough to meet the number of spells the class can typically cast, increase the total SP by 1/2 its HD.
Increasing SP with level advancement
When a character levels up, he gains SP in the same fashion as he gains HP, through rolling his HD once. The resulting number is added to his SP. However, you cannot roll the HD for both his HP and SP simultaneously; his HP and SP should vary and doing so would only be lazy.
Limits to using the SP Spellcasting Variant
Due to the difficulty of converting Spells for this system and all, this variant should be used as a base creating classes that do not abide by the same rules as other spellcasters and have very few spells that can be categorized into spell levels.
This being said, for DnD Wiki's sake (and its administrators'), please still create spells that would use the SP Variant as though they were normal spells(as in the categories if possible). I don't want to give the poor administrator trouble of sorting through level-less spells without a home. If you can, try to refer to classes spells in full detail in the classes description if they are few and easily explained.