EDIT/PS: I totally HATE D&D's magic system, though, and would totally revamp it entirely. I'm currently working on an effect-based magic system that uses power points instead of spell slots for my own version of d20.
Sounds neat, you gotta basic framework you wanna share or is it still under wraps?
I'm still working out the kinks, plus some details might be specific to may own variant of the d20 system. But the basic idea is I'm defining all basic effects, like damage, healing, conditions, etc., as universal effects used to build powers, objects and hazards. Most effects follow simple criteria based on common characteristics. Damage is 1d6/effect level (save for half) for Instant Damage, for example, and conditions have a save DC of 8 + effect level, etc. An effect's level is equal to the level of the power, object or hazard generating it. Power Levels are divided by power category (Natural, Magic, Martial or Trained) and are based on your class and level, and modified by a related ability score.
Effects also have certain specifications, including Range, Duration, Advantages* and Limitations*. Ranges are divided into Self, Melee, Ranged or Area (Aura, Cone, Cubic/Spherical or Line), are balanced against each other (self and melee get a +1 effect level bonus, Ranged has longest range, Area types have shorter range and affects everyone, friend or foe), and range distance is increased by effect level. Duration is specified by the effect type and can be Instant, Timed (1 round/effect level by default), Sustained (consciously maintained) or Permanent (usually counts as multiple Advantages). Advantages improve the effect somehow, such as increasing its range/area (in doubles), making area effects discreet, increased duration (by one time unit: rounds, minutes, days, weeks, etc.), extra effects, etc. Each advantage requires a Limitation, such as increased power point cost (default for magic powers, unless caster has other ideas and GM allows it), increased Activation DC, increased activation time, cooldown periods between use, etc.
Access to magic is defined by various Effect Pools that have a certain theme and determine the types of effects you have access to. And specific effect and spec combinations have to be learned as Spells to be used effectively. Attempting to use an unknown spell is possible, but increases the power's Activation DC by +5, and increases its activation time by one time unit (standard action to full-round, full-round to one minute, etc.). Effect Pools may vary by setting and GMs may make up their own, but I have two types of pools developed so far to layout the basic groundwork and provide universal functionality applicable to most fantasy worlds. These types of effect pools include Domains and Incantations.
Domains handle your command over different aspects of reality. They are divided into six Spheres, containing two Domains each: Artificial (Creation, Enchantment), Dimensional (Space, Time), Elemental (Energy, Matter), Mental (Psychokinesis, Telepathy), Primal (Animals, Plants) and Vital (Death, Life). Incantations are focused on general categories of common effects, such as damage (Harm), bonuses (Bless), conditions (Curse), extrasensory effects (Divination), etc. The Harm incantation, for example, provides access to all damage effects in general, while the Energy domain would provide access only to energy damage (fire, cold, electricity), and the Telepathy domain would have access only to psychic damage. Energy and Telepathy would also have access to other types of effects as well, however, such as conditions (Blindness, Deafness or effects that control elementals for Energy, mental conditions for Telepathy), summon effects (elementals for energy, psychic creatures for telepathy), extrasensory (detect energy or elementals for Energy, mind-reading for Telepathy), and other stuff, while Harm only has access to damage.
The GM may determine which types of pools they allow, and restrict an entire type of they feel that they overlap or conflict too much. Or they can make up their own using Domains as a basic guideline (basically develop an underlying theme, and pick which effects are related to it by going through each effect category, which currently include: Aid, Conditions, Creation, Damage, Extrasensory, Healing, Restore, Traits, Transform and Travel).
*Names pending change, since they sound too much like character abilities, but basically the idea you can add extra stuff to a basic effect.
EDIT: Also forgot: Powers cost 1 power point to use by default, +1 per increased power point cost limitation selected, and may require an Activation Check, with a DC of 10 +5 per Advantage possessed by the power's effects. Some effects may have level requirements, and particularly high requirements count as selecting an Advantage.