A character class in 3rd Edition D&D.
The Spirit Shaman is a variant form of the Shaman class that has been made more "mainstream" since it's predecessor was first printed in Oriental Adventures and consisted mostly of a combination of elements of the Cleric and Druid classes.
The writers decided to go for a different avenue with the Spirit Shaman instead and make it completely unrecognisable from the previous version.
This one has much more of an rugged, outdoors-y feel to it. It has better fortitude saves, more spells per level and LOADS more supernatural abilities, though all designed to deal with "Spirits" (defined as Incorporeal Undead, Fey, Elementals and anything Astrally projecting) but impressively, they gain a spell like ability that can be used to Raise Dead with no penalty to the target. Eventually Spirit Shamans end up transcending the mortal world and become Fey. In fact at first level, they assign themselves a Spirit Guide which later gives them the ability to do various things, such as Detect Spirits for them (unlike the regular Shaman's ability to just "see" spirits), allow them to resist enchantments and eventually can do the concentration on spells for them if they are too lazy to do it themselves.
One unusual thing about the class is that while they are officially spontaneous casters for qualifications, they "retrieve" their spells known at the start of the day letting them change their spells up. This helps them cure conditions between adventures better. This would become the standard system for casting in 5th edition.
Playing a Spirit Shaman
Is the class worth it? It depends, while it does have more spells per day the class actually casts spontaneously like a Sorcerer does and in fact only knows a tiny amount of spells from the Druid list (only 3 per spell level in fact). Though the Shaman is allowed to change the selection each day by communing with their Spirit Guide, that still leaves the character very slim on utility.
This is essentially what kills the class, as by comparison a Favored Soul cast the same number of spontaneous spells-per-day as this class, but knows up to six of each level instead of just three. If you could just cast the Whole List spontaneously that would have been awesome but the limitation means that regardless of being able to change the three each day, you will find that they inevitably end up spamming spells the same way that a Warmage does, but since Divine casters don't have as many damage dealing spells, the need for multiple uses of status effecting or social spells becomes unnecessary unless your player can think outside of the box in his approach to tactics. If your campaign is not combat focussed, then you were probably better off playing something else anyway.
Unfortunately that suggests that the best use of the Spirit Shaman class is for transitioning into something else, but unless a new class has it's own spellcasting progression your character is unlikely to have the sheer daily spellcasting versatility of a proper Shaman, or a Druid or Cleric.
Even as for a dip level for those that just want some minor spellcasting powers without interrupting their primary class progression much, a single level or two of Spirit Shaman does not you any amount of low level freedom that a different class could not already give you either. It really depends upon your attitude to the Spirit world in your campaign then. But if you're in it for the class features, then you're better served remaining in this class to it's completion, since the class features are it's strong suit.