I spent a week in Haiti last year, and would say it was definitely a worthwhile experience. If for no other reason, it opened my eyes to the day-to-day situation of a large part of the world, and made me much more appreciative, intentional, and less wasteful of the relative prosperity that I have been granted.

Even though my work was with a religious organization, I hope that you'll find my notes helpful. The organization I was with runs an orphanage/feeding program/clinic in a very rural part of the country. Officially, I was traveling with a journalist helping him to document what the organization was doing there, although I also did some other random "hands on" stuff such as fixing a 4-wheeler, taking food to families in the community, and hiding easter eggs for the orphanage kids to find.

We stayed at, what can best be described as a compound, which was open during the day to locals (since it housed a clinic). The compound had dining and sleeping areas as well as it's own generator and water purification facilities, which was great given that we were in an area which does not have electricity or clean water. The organization I was with handled all of the transportation, both within and outside of Haiti, and also made sure we had all the proper shots, malaria pills, etc before we arrived.

Since we were in a rural part of Haiti, I can't say there was much in the way of tourist sights to see, although the organization I was with did offer day-long "excursions" to some of their projects in other parts of the country, in order to give you a broader picture of Haiti. Haiti does have some more "touristy" areas near the major cities, and if you were traveling on your own I'm sure you could find places to go for a day.

I can't say I ever really felt unsafe there. In the rural areas, a white person is pretty high-profile and the attention may work in your favor. That being said, knowledge of the language helps, so venturing too far out on your own without a local guide is asking for trouble. The organization I was with employed a few locals for just that purpose. I'm also told that the larger cities (Port-au-Prince, etc) are considerably more dangerous, as one would expect in any major urban area.

I can't speak for other countries, but with Haiti, the biggest concern I would have is medical. Some major organizations bring in their own medicine/supplies from the States and have trained medical staff on site. Try to get on with one of these. I would not want to get sick there and take a gamble with the local hospital system.

I think volunteering is a great way to spend your vacation, at least once. Good luck!