Tropical Foods (2101 Washington St. in Roxbury) has been mentioned a few times regarding ethnic ingredients, and I finally got a chance to check it out. Lots of interesting ingredients although I thought it had more African/Carribean products than Latin (for example, no flour tortillas and only one brand of corn). Seeing all the unfamiliar ingredients made me want to experiment with that type of cooking.
Some quick things I noticed - Lots of Carribean-influenced spices, jerk marinade, hot sauces, etc. including Caribean coffee. I've never seen so many potatoes and yams - huge selection with malanga, negro yam, Taro/dasheen, Cuban sweet potatoes, etc. Fresh meats, lots of fruits and vegetables, and a large bread section. I picked up some sour oranges and a pork shoulder to make carnitas, mangos, plaintains, dried chilis and spices, and frozen empanada dough. They also had a large variety of tamarind - the paste, the concentrate, tamarind pods, and even tamarind candy.