We have sent a barrel to my husband's family and included the following - tins of tuna, salmon, sardines (in tomato sauce), shrimp, corned beef, etc., tomato paste, tomato sauce, spaghetti sauce, tins of beans and bags of dried beans and lentils, powdered milk, tins of fruit, dried salt cod, toothpaste, various types of pasta, Kraft dinner, couscous, cocoa powder, powerdered drink crystals, bags of spices, ketchup, maple syrup, pancake mix, oatmeal, tins of Carnation evaporated milk, tins of coconut milk, flavoured coffee (since they arlready have the best coffee available), tins of corn, peas or potatoes, tins of canned pasta and soups, boxes of Liptons chicken noodle soup (powdered mix with dried noodles), chicken and beef boullion cubes, deoderants, baby powder, bars of fancy soap, anything from the dollar store (ie. plastic plates, cups, tea towels, candies, kitchen utensils, colouring books and crayons, coloured pencils, school supplies like calculators, bound three hole lined paper books, barbies, pens, pencils, stickers for kids, yoyos, chalk, tin foil, etc.), cheap flip flops from Old Navy, any clothes from my husband and I that are too small or we don't want anymore, sewing supplies like thread and needles, over the counter pills like Advil and Tylenol, Band-Aids, Glad resealable baggies, tape (scotch, packing and duct tape), resealable plastic microwavable containers, perfume or cologne, make-up, books in English and anything else that is non-perishable and you can stuff in the box! We did not send any rice or white sugar because it's widely available and weighs a lot in the box. Also, when buying things in the grocery store, remember that everything is going to weigh a lot and will crush things like cereal and crackers, etc. Buy oatmeal or pancake mix in a bag. Going to a bulk store to buy things like nuts, oatmeal and flour is also a good idea but make sure to double bag. Trust me, they will be over the moon with any of the above items. We also like to throw in a few items that they may not be able to get in the DR (food things) and they are excited to try new things.
The cheapest way to do a box (as we learned when we tried to fill it in the course of one week) is to get the box/barrel and leave it in your home for several months and every time you go shopping, buy a few extra things to put in the box otherwise you could easily be looking at several hundred dollars to fill it. If it's a box and not an actual barrel, make sure you tape it first before you put anything in it and just leave one end open that you can close and tape up once full. Use duct tape instead of clear tape because it's stronger.
Hope that helps and good luck.