I use Transexpress.com which uses Vimenca here. You can register at transexpress.com with your address in the DR and they'll set you up with an address to mail to; you can also give credit card information so you do not pay on arrival. Their turnaround time - from Miami to here (I'm on the North Coast) is very fast. I just ordered something, arrived in Florida on Fri, and it'll be in Sosua on Monday. Not quite as fast at holiday times or high season, but very reliable. They have a knowledgeable office in Miami you can call for information; or their site for rates. The heavier the package, the cheaper per pound.