ProWorld

ProWorld has a great variety of volunteer, internship and study experiences in many different countries- many focused on Central America and South America, but also India, Nepal, Ghana, and Thailand.


The study aboard programs mostly are language immersion, service-learning, and field study programs at local universities.

Many of the internships are very unique to the culture and location. For example in India you can do a health internship at a ashram! or in Mexico help kids with disabilities ride horses. Have to say...that's pretty cool. 


They also have scholarships for certain projects and referral incentives. 

Proworld

Global Vision International

This is another organization that provides flexible and customizable abroad experiences. There are volunteer and internship opportunities that can last as little as 2 weeks or as much as more than 6 months. They have projects offered on very continent (except for Antarctica). They also have "expeditions" which seems to be a combination of volunteering and tourism with a group, they mostly focus on environmental and wildlife themes but there are community expeditions.

http://www.gviusa.com/

Volunteering: 

• with Children (teaching, arts, sports, social work, childcare)
• climate change 
• marine conservation
• Teaching English abroad
• Construction
• Community
• Wildlife and Conservation

Internship:

• Environmental
• Non-profit
• Humanitarian
• Responsible Business

ABroader View

One of many many volunteer programs out there- this one interestingly offers specifically "Social Welfare" programs (as well as law, child care, language immersion, and more) - however the SW programs are concentrated in Central and South America (and 1 in Africa).

If you are interested in doing some social work in

• Chile
• Peru
• Costa Rica
• Ecuador
• and Tanzania

Check out Abroader View

i-to-i Volunteer and Adventure Travel

This seems to be more of those organizations that "work hard, play hard" - combining some volunteer serving with tourist activities.

They specialize in offering TEFL (Teaching English as a Foreign Language)

They offer programs by the week up to 12 weeks, but they also have some special internships every year for 2011 it's for China and Thailand.

http://www.i-to-i.com/