Create Doll - a skill you'll get on the Sword Coast if you join the Natives (see: The Ancestors' Blessing). You won't be able to complete the game without it: there are a lot of times when you'll be creating doll to gain control over non-playable characters. Apart from that, the skill will also let you create dolls with curses, which are sadly very weak. Requires Voodoo at 1.
Create Sceptre - not a particularly useful skill, available only to the Natives' allies. Scepters can be bought from most of Native traders, but their effect leaves much to wish for. Don't bother with it. Requires Voodoo at 2.
Brew Potion - potions are easily available, so brewing them misses the point. The only argument in favor of this skill is that it allows for creating potions which permanently raise the statistics. The catch is that ingredients are very rare and the benefits - not too high (the bonus is usually +2 as opposed +1 in the case of raw plants). The skill is available to both factions. Requires Voodoo at 4.
Create Talisman - another useless skill - there is an abundance of all kinds of amulets and talismans on the world map, so the ability to create them becomes utterly pointless. Another issue is that recipes and ingredients are very expensive, making it pointless even more (it's available only to the Natives' allies). Requires Voodoo at 6.
Powerful Curse - increases the power of cursed voodoo dolls. Since they are completely uneffective, you can go ahead and ignore it (available only to the Natives). Requires Voodoo at 8.
Voodoo Master - reduces the regeneration time of voodoo sceptres. The skill doesn't work - same all the others which affect cooldowns. It's available only to the Natives' allies. Requires Voodoo at 10.
Black Magic - increases the power of curses and sceptres by 5 points for each skill level. Since both items are radically ineffective, ignore it. Subsequent levels of this skill require Voodoo at: 3, 6 and 9.
Death Cult - increases the power of a summoned spirit by 5 points for each skill level. There is only one spirit to "gain", and it's not very helpful - so go ahead and ignore it. Subsequent levels of this skill require Voodoo at: 2, 5 and 8.
Ritual - increases the Ritual talent by 5 points for each skill level (affects the power of potions). It only pays off if you can't help yourself and keep swallowing all kinds of stuff. It doesn't affect liquor! Subsequent levels of this skill require Voodoo at: 1, 4 and 7.