Sounds great!
Of course Habitat for Humanity builds houses at cost with families in need around the world - over 60 countries and in their 25th year or so by now.
Transformational Journeys is another non-profit (based in Kansas City, MO). They take folks on "reverse mission trips" to a variety of places such as the Dominican Republic, Guatemala, Brazil and Kenya. "Reverse" meaning that the folks going on the trip have the intention of serving others, but end up being served themselves by the changes that occur in their hearts by helping those less fortunate. You can email Dan Hickey, President, at journey@qni.com for more information.
Both these organizations offer short-term mission trips of two or three weeks in length (or longer if you want to commit three years to Habitat).
All of my efforts over the past seven years have been concentrated in and around Barahona: building houses, schools, clinics and working with children. I lived near Barahona for a year five years ago (my longest stay) and volunteered with an organization based in both Sarasota, FL and Gloucester, England called Community Partners (COPA). They operate schools and clinics in two villages (one Dominican and one Haitian) near Barahona.
No matter what the service is that you provide, I think the Dominicans I've worked with, more that anything, feel a sense of hope by our presence. And it's a great joy to know that you're doing something to make life better for the people who live in such a beautiful place.
I could obviously go on and on! Send me a personal email if you like...