The Haitian gourde HTG is the currency of Haiti.
As of April 2014, the exchange rate was USD1 = HTG48.85
Although merchants are required to quote prices in gourdes by law, virtually everything is priced in "dollars"--not US but Haitian dollars, equivalent to 5 gourdes. This practice is a holdover from the US occupation of Haiti in the early 20th century, during which the gourde was pegged at 5 gourdes to the US dollar.
Haiti has become famous for its very informal yet interesting bustling marketplace. Everything is sold here ranging from the curiously appealing to the dullest of objects for rather inexpensive prices. Haggling is both wise and recommended, as most Haitians will charge foreigners at least double the market rate. There are various large retail supermarkets in the capital that offer a variety of items at fixed prices. Haiti has a world of crafts waiting to be sought after.
You will best be able to find stores and legitimate shops in certain hotels and resorts.