There are many ways to volunteer while you travel, and they all require some advance work. You can start one of two ways.
Pick A Destination
Choose a destination and then look for opportunities to help in that area. If you are already planning a trip, and know that you have the time to spend volunteering in that area, you should go online and look for organizations at your destination and get in touch with them. Many organizations have volunteer programs in place that require a minimum commitment in terms of time. When I lived in Roatan, Honduras, the clinics on the island were understaffed, and the closest one to me had one full time doctor and relied on visiting Doctors from Washington State who volunteered for periods of time from 2 weeks to 3 months. I have personal experience with the generosity of the volunteer doctors. It was a visiting Doctor from Seattle who figured out that I was having heart problems, and told me to get off the island and see a cardiologist!
Pick A Cause
Think about what you have to offer and match it up with a cause, like education, health, or construction, and then contact organizations until you find a place you want to offer your help.
My parents, for example, are retired and enjoy traveling in their RV. They were looking for a way to volunteer while they travel around North America and a friend introduced them to Habitat For Humanity. This organization has projects going all the time and usually it is local volunteers and the recipient of the home that do all the work. However, there is a mobile support group called the Care-A-Vanners that do house construction, roofing, interior and finish work, renovations, and disaster relief. Usually a Care-A-Vanner group will descend on a project that is near completion, after the recipient of the home has put in their mandatory work hours on the project. A group of Seniors in RV’s may not sound like a construction foreman’s dream team, but the skills, experience, and enthusiasm they bring to a job site are extraordinary. The volunteers pay their own expenses though they usually get discounted parking for the RV. The best part is that they often get to participate in the handing over ceremony where the recipient of the home gets the keys. My parents said that even when you are working shoulder to shoulder with the recipient on a build, you don’t realize how incredible a gift it is until you hear their story and know how much sweat equity they put into the project.
A good friend of mine is a nurse, and over the past several years she has been documenting her efforts to raise money so she can continue to volunteer her services. So far she has volunteered in Pakistan, Liberia, Benin, and on the Mercy Ships. In every case, she is required to cover all of her expenses which can be quite considerable when traveling such great distances. She has recently spent a year learning to speak French so that she can take a long term volunteer position in Togo, West Africa. You can read more about her journey here: http://www.nursejodi.abwe.org