Random things a non-evil Necromancer could do, while staying within the themes of life-energy transfers and spirit manipulation;
Your best bet for an effective good necromancer is to research some necromancy spells of your own.
Necromantic energies are great at killin' stuff. Some stuff *needs* killin', such as hostile organisms, contagions and parasites. A Necromancer makes a *perfect* source of arcane cure disease, by sending a tiny flood of negative energy washing through a living person’s body, sickening them and inflicting a point of ability damage to Con, but kill all of those pesky less-than-one-hit-point diseases and parasites. (The sickness and ability damage? Well, some of the stuff killed might have been helpful gut bacteria. We takes the good with the bad...)
The same feature makes negative energy useful for sterilizing an area, for purifying tainted water, for purging foodstuffs of contagion, etc. in a magical medieval version of shooting radiation into food to kill bacteria. And there are people who will pay good money to be 'sterilized' for a short time, such as high-priced prostitutes, noble brats who want to party with the hoi-polloi without 'consequences,' etc. If you want to go with science, a flood of negative energy to kill reproductive cells would render a woman infertile until her next cycle (which, if that time is uncertain, would be in the next 2d8 days), and a man infertile for a day or two (6d8 hours?). Alternately, we can toss science out the window and have it last 30 days, regardless of gender, 'cause it's magic, and the spell is actually leaving a charge of negative energy in the person's body throughout the duration, making it a reliable and affordable form of magical birth control.
Contacting spirits of the dead, the actual original role of the 'necromancer,' could allow for a wide array of benefits. The spirits could be consulted for lore, allowing for bonuses to knowledge checks, they could be consulted for assistance in skills they have mastered, allowing a spirit-caller to possibly 'Aid Other' on skill checks of all sorts, by contacting the appropriate 'spiritual advisor,' and they could even, if made manifest, however weakly, be called upon to provide other benefits, aiding a particular target as if using the Aid Other combat action, as the young warrior feels the spirit of a grizzled veteran flow over him like water, lending skill to his sword-arm, or pushing his shield up in the way of an oncoming blow. This sort of thing would be a fine low level buff, since it's only giving the recipient a +2 to attack rolls or AC, switchable round by round, as the spirit of the deceased soldier provides tactical advice from within the beneficiary, temporarily 'possessing' him.
Spirits of the dead also make superior scouts, perhaps having only a single hit point and being easily dispelled back to the spirit world, but being able to pass incorporeally through surrounding walls and doors to observe what is on the other side. At low levels, the necromancer has to find (and bargain with!) a local spirit, so that he might only be able to use this spell if he can find a suitable corpse. At higher levels, he might be able to bind such a scout to him, perhaps as an Improved familiar, using Shadow stats (but not evil and with no Create Spawn ability, resembling a translucent black and white image of the person from whose body it was conjured), and have it follow him around (and return in 24 hours, like a ghost, if 'dispelled' by damage or turning or whatever). The spirit *might* be a very weak ghost, of someone who refused to pass on, for whatever reason, but, more likely, would be one of those spiritual echoes that get left behind in a corpse, with which one speaks when casting Speak with Dead, and while the necromancer has a 'fetch' of the person, their actual soul is off in Nirvana, counting turtles or whatever. At higher levels, a necromancer can barter with and bind one of these 'fetches' into a spirit jar or something, and bring them around with him, opening the jar when he needs their services, instead of having to find a convenient body at the target location. These jars would usually be one-use items, with the spiritual fragment free to return to its resting place when the service is over, but higher level versions would be re-usable, perhaps containing the ashes of the deceased (or even being crafted from their skull!) as an 'anchor' for the echo.
One step beyond conjuring souls, or these 'echoes' used by the Speak With Dead spell, a necromancer could use *his own spirit* for such things, sitting down cross-legged on the ground and shaking and rolling his eyes back as his own spirit travels forth with Shadow-like stats, to scout an area, or even to attack people. If his own spirit is 'slain' or dispelled, he suffers some traumatic result (dropped straight to -1 and Dying, for instance), so he's ill-advised to send his *soul* out to kill people...
He could also project a fraction of his own life-energy, necromantically, into unliving matter, allowing him to animate objects, similar to the Animate Objects spell, but one item at a time, and with the HD limit dependent upon his own power (the 'strength of his soul'). The low level version of this spell would, again, require him to send his soul out of his body, to 'possess' the object, but at higher levels, he could cast a spell that infuses an object with a fraction of his life-force, and allow him to animate it while remaining active himself (albeit at reduced hit points, as some of his life-energy is animating the object). If the object animated is destroyed, he loses the hit points he sent over to animate it (instead of flat hit points, I'd make it cost Con points, 1 for a smaller item, 2 for an item of his own size, etc.), and would have to recover the lost life-energy through healing, either over time, or through magic. Perhaps he can project life-force into anything, and animate it, or perhaps only into substances that were formerly alive (things made of bone, wood, leather, etc.). Perhaps the item needs an association with death (graveyard soil, animated by the necromancer with the stats of an earth elemental of appropriate size, or a weapon, functioning as a dancing weapon while he's 'possessing' it). Whatever seems thematically appropriate.
By projecting his life-force like this into another person, he could heal them, starting at a one for one ratio, and, at higher levels, learning to more precisely control the healing effects, and healing another of 2 hit points for every 1 that he takes, or something similar, doing a kind of magical transfusion, where he floods the wounded person with his own magical life-energy, to reinforce their body's own healing rate.
Less benevolent applications could allow him to project a fraction of his spirit into another, like a weak version of Magic Jar, allowing him to spy upon them as they go about their business, peering through their eyes, and hearing with their ears. At higher levels of this effect, he might be able to influence their actions, to a limited extent, or even totally seize control of them, lurching their body around like a puppet, if his soul can overpower their own. In a less sinister vein, he could perhaps perform the same 'buffing' service of the lesser spirits he used to call up, 'back in the day,' and from within an ally's body, warn them of danger, inform them of knowledges that he possesses, or even guide their limbs in battle, giving them the benefits of Aid Other. This more benevolent 'Rider Within' spell wouldn't allow him to seize control, or to perform actions like spellcasting through his 'host,' and his own body would remain in a death-like trance during the spell, as his animus is out to lunch.
Earlier editions made decent use of Feign Death type spells, another necromantic staple, and while not a 'cure' spell by any means, it can help someone survive poison or the effects of starvation or bleeding to death, by putting them into a deathless trance until they can be gotten to a safe place, or to someone who does have the cure needed to prevent their death.
The majority of a good necromancer's effects should work similarly, using *his own* life-energy to animate things or heal people, using his own spirit to scout places or inhabit things, and perhaps using his mastery of life and death to help others resist effects, by giving them immunities similar to those of undead (infusing someone with extra life-energy to make them resistant to environmental cold / heat effects, for instance, or suppressing their bodies need for air, so that they can go without breath for a short time, or making them incapable of bleeding, etc.). When he does call up spirits, they should be bargained with, or represent the 'echoes' that one contacts via Speak with Dead, not souls dragged screaming out of Heaven (or Hell), which should be way, way beyond the beginning Necromancer's purview (and terribly unsafe, since Asmodeus, for one, takes a very dim view of people taking things that belong to him!).
This 'bargaining' should occasionally include it's own Side-Trek, as the spirit you wish to interrogate about information promises to tell you everything, so long as you go make sure her family is safe, or that the bastard who killed him is punished. Unlike a divination spell, which 'just works,' negotiating for the services of a spiritual scout or advisor may occasionally require some extra effort.’
For a more shamanistic take, a 'primitive' necromancer may even learn spells that call up the spirits of animals, infusing them into the spirits of his tribe's warriors, who streak their faces with blood and ash and wear the skins of the animals whose abilities they seek, so that when they go to the hunt, they have the keen senses of their 'benefactor,' or the savage nature of the bear, etc. Yet more 'necromancy buffs,' only, in this case, using the life-force and spiritual residue of animals to empower allies.
