Global Volunteer network provides excellent low-cost international volunteer opportunities. They have volunteer programs in countries all over the word including Latin America, Russia, Africa and Nepal. Global Volunteer Network can be less than half the cost of similar volunteer organizations in their host countries. If you are interested in volunteering abroad, check out their website. Volunteer abroad with Global Volunteer Network
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This post has been getting quite a bit of traffic recently. I volunteered in La Esperanza, Honduras in 2007. I worked at the local hospital and started some public health education programs. You can read more about my project here, and here. I actually volunteered with another international volunteer program, I-to-I. However, Global Volunteer Network was offering identical programs (or better programs that included more language training) in the same town for about half the cost as I-to-I. So, if you are thinking about volunteering abroad, I definitely recommend that you check out Global Volunteer Network. You can also read my post about volunteering in Latin America. If you are planning on volunteering in Honduras, the Volunteer’s Guide to Traveling in Honduras is also worth a read. A friend of mine, Christa, volunteered with GVN in South Africa in 2009, and she also documented her experiences on her blog.
You can get to 
Erin Miller 
I don’t know about Global Volunteer Network. They look good but an alternative is Help to Educate who are a registered charity in the UK and Nepal. They are unique because:
1.) They are a registered charity in Nepal & work with local village schools and hostels and ask them to select applicants on the basis of need.
2.) Volunteers are placed in schools and hostels with children who would not ordinarily get the opportunity to practice and improve their spoken English. Just speaking and interacting with English language speakers increases their confidence in the language. They take their exams in English so its a big help and makes a big difference.
3.) The donations the charity receives goes towards funding the care and education of former child labourers. Thus, volunteers double the impact they have when they go to Nepal. Not only are they helping the local community but they are also giving children from extremely poor backgrounds the opportunity to study in school. For example, we were able to establish Little Gems Hostel due to the donations we received from volunteers.
4.) They show all volunteers the work that they are doing in Nepal.
5.) Schools and hostels are extremely grateful for having the opportunity to host English language speakers from abroad and see tangible benefits from having volunteers.
Take a look here-
http://www.help2educate.org/index.php?tab=Teach-in-Nepal