Haiti was something of a failed state even before the Earthquake. Its leaders had stripped it of natural resources to fatten their own pockets and left the people to suffer. As the article points out, there was no mental health system even before the quake, and now the ratio of trained psychiatric help in the country to population is about 1 to 1 million. So people turn for help wherever they can get it. Here I should mention the ongoing stigma of mental illness in the world, even in the Western world, and how bad it is for society. There are large numbers of adults who suffer from some form of it, impacting the lives of everyone around them. Treatment, real treatment and not just drugs (not that drugs do not have a place, they do, but not alone) is hard and few understand the amount of effort and time it takes to deal with some of these issues. But you did not come here for my mental health rant. You came here for me to rant about religion.
Vodou refers to a composite faith that takes traditional elements of West African culture and merges elements, sometimes only minor, of Catholicism formed in the wake of the slave trade and the merger of of various African peoples and forced conversion. Throw in a strong dash of European occultism and shake well. Adherents believe that their is a supreme good God, but one that does not intervene in human activity, and they instead worship the Loa, or spirits, that are subservient to the Good God. Each Loa is responsible for some aspect of life. Communication, appeasement, and possession by these Loa are necessary to keep the spiritual forces in life in harmony.
There are as many types of vodou as there are communities that practice it, as one might expect given its origins. Overall the faith preaches against dishonor and greed and the need for love and community. Each community is led by a Mambo (female priest) or Houngan (male priest) responsible for leading the rituals and providing aid to the community. Most notable is the ecstatic dances, often the culmination of days of preparation and ceremony. In Haiti these are often formal gatherings while in the US they can have a more party like atmosphere.
Evil sorcerers are known as bokor and are the source of many of the popular images of vodou. They are the ones who are said to create zombies and send curses. The so called "voodoo doll" is associated with New Orleans and something known as HooDoo, or conjuring. This is more of an occult practice than a faith system, although there is cultural overlap with vodou. The doll may originate in the nkisi of Central and West Africa, and object ritually made to be inhabited by a spirit.
If you want to know more about the subject check out What is Hatian Voodou? and the links that article provides.