Kindly Necromancers

[Varyon]

First off, you need a society where necromancy isn't perceived as evil. Once you've established that, you have all manner of uses for whitehat necromancers. EDIT: I should note that not all of the below need to be socially acceptable - choose which are, and this will help dictate the role of whitehat necromancers in your setting.

Labor: Undead would make for a good source of labor. To make this more palatable, it could be a punishment for criminals, and/or the living could sell the right to animate their bodies when they die (the latter could be in the form of recurring payments to their families). Necromancers would be the ones animating and controlling such a workforce, and would also be in charge of maintaining the bodies and making certain nobody does anything unethical with them. Note this works best if there's a way to prevent rotting and the like, as otherwise you're just begging for widespread disease in the living. Cleaning the bones and putting the animated skeleton into some sort of suit that makes it substantially less terrifying might be a good idea.

Speaking with the Dead: This traditional role of necromancers could have all manner of uses for the good of society. Aside from simply allowing clients to have words with their departed loved ones, this would also be very useful for solving murders and the like. This could be combined with the above as well - a man dies in the prime of his life, the family has a necromancer converse with his spirit and get official permission to sell rights to reanimate his body, allowing him to continue to provide for his family beyond the grave.

Final Rites: In settings with "naturally" occurring undead, necromancers might preside over funerals and perform the final rites/etc that prevent the newly deceased from rising as such. Necromancers are also uniquely equipped for combating the undead, as they have a good deal of power over them. This is somewhat diminished in settings where healing magic and the like harms the undead, but even then necromancers have an advantage - a cleric/white mage can cast a spell that destroys an advancing zombie, but the necromancer can turn that zombie into an ally that turns around and takes out one (or more, if he chooses an above-average specimen and/or bolsters it) of its former fellows. Even without naturally occurring undead, if there are hostile necromancers about (and, humans being human, there certainly will be) the good ones can help combat them.

Your Face Asplode: Less on the "kindly" side, in some settings necromancy can be quite effective against the living. Whitehat necromancers can serve as soldiers in the military, as bodyguards for important people, or even as law enforcement (most police are armed, after all), leveraging their magic to kill or disable threats. Note that even if necromancy cannot directly affect the living (or does so in a manner unbefitting of a good character), they can leverage their abilities from the first three categories to serve in such roles.