When I read through Book of Exalted Deeds once again, I came up with a question:
Can a true neutral cleric cast sanctified spells?
While the book explicitly says that evil ones cannot cast such spells, it doesn't say anything about the neutral ones.
[RPG] Can a Neutral cleric cast Sanctified Magic
clericdnd-3.5e
Related Solutions
A cleric cannot cast spells with an opposed alignment descriptor
Taken from the Cleric description in 3.5 SRD - similar rule appears in PHB:
Chaotic, Evil, Good, and Lawful Spells
A cleric can’t cast spells of an alignment opposed to his own or his deity’s (if he has one). Spells associated with particular alignments are indicated by the chaos, evil, good, and law descriptors in their spell descriptions.
So as an evil cleric, or a cleric of an evil deity, your character is forbidden from using any [Good] spells.
I'm not aware of any rule prohibiting an evil cleric to cast spells with the [Light] descriptor.
Regarding spell descriptors...
I recommend you read the SRD text about spell descriptors. It isn't very long, and says (among other things):
Most of these descriptors have no game effect by themselves, but they govern how the spell interacts with other spells, with special abilities, with unusual creatures, with alignment, and so on.
For example, spells with the [Good] descriptor have special effect on certain evil outsiders, can't be cast be evil clerics, and can be detected using the Detect Evil spell. Similarly, some creatures (mostly undead and darkness-themed) are more vulnerable to [Light] spells.
Worldly Focus
Weird name for the effect, but this feat from Faiths of Eberron allows you to cast cleric spells without a divine focus. Note that it does nothing for turn undead, or any other usage of a holy symbol, which seems like an oversight to me but then so too does the lack of holy symbol in Vow of Poverty exceptions. But then, who actually uses turn undead to, ya know, turn the undead?
Summon Holy Symbol
I had originally suggested summon holy symbol, as follows:
An orison from Complete Champion that does what it says on the tin. Since the summoned holy symbol is a temporary magical creation per the Conjuration (Summoning) rules, it has no value and so (arguably) should not count as a “material possession” and cause trouble for a cleric with Vow of Poverty. This is a real holy symbol that can do everything a holy symbol can, but only lasts 1 round/level.
However, careful reading of the Conjuration (Summoning) rules indicates that summoned objects—unlike creatures—do not go away when the spell ends “unless the spell description indicates this.” Note that, even in core, there are no Conjuration (Summoning) spells that seem to remember this rule: summon instrument reads almost exactly like summon holy symbol, for instance. This makes absolutely no sense, but that is what the rules say, both in Player’s Handbook and Rules Compendium. My guess is that this rule was intended for instant summons (which, unlike most summoning spells, brings a particular item with your arcane mark to you) and maybe secret chest (which has its own special rules anyway), but it’s in the general Conjuration (Summoning) rules, not in the description of those spells. As a result, since summon holy symbol says nothing about the holy symbol disappearing, rules-as-written this orison can just create a permanent holy symbol out of thin air, and its round/level duration is meaningless since nothing happens once the duration ends.
That means the summoned holy symbol is no longer temporary, and there is no particular reason to think it should be value-less (Complete Champion indicates that it is not “particularly valuable” but that seems more to mean that it is the ordinary 1-gp holy symbol rather than one of “particular” value, rather than a holy symbol that is literally worthless). It is therefore difficult to argue that this spell is safe for those with Vow of Poverty.
Best Answer
It Depends on the Cleric's Deity
The cleric's class features include the class feature titled Chaotic, Evil, Good, and Lawful Spells, which says
Emphasis mine. Thus a neutral cleric of an evil deity could not cast spells with the good descriptor, and that includes most sanctified spells. A neutral cleric of a neutral deity could cast sanctified spells (but might be reluctant to do so or might follow that by casting corrupt spells to preserve the balance), as could a good cleric of a good or neutral deity.
As KRyan's Comment pointed out, "A cleric may not be neutral unless his deity's alignment is neutral" (PH 31), so there's just no such thing as a neutral cleric of a good or evil deity.
The Eberron Exception
It bears mentioning that the Eberron Campaign Setting text loosens the above restrictions as follows:
Sanctified spells, however, remain exclusive to good and neutral clerics of good and neutral deities: "Evil characters cannot cast sanctified spells, including ones cast from magic items" (BE 83).