I have one year
1. Idealist.org has an excellent list of organizations that have one-year programs, so please visit this page and start clicking.
2. Tostan is an organization based in Senegal, West Africa. It is dedicated to educating and empowering Africans who have had little or no access to formal schooling. They work mostly in rural regions. The founder, Molly Melching, began work in Senegal in the 1970's and the organization is currently expanding to meet increased demand across Africa. They have opportunities for you to volunteer for one year or more. It does help if you speak French for this one. You'll want to read the whole site, of course, but click here to read about volunteering for this fine organization. Oh, and Tostan means "breakthrough" in case you were wondering!
3. This one requires commitment which is why it is in this category. It won't take a whole year of your time, though. You can still work, study etc. But if you can commit to a period of time, please check out MENTOR, which is a clearinghouse and a support organization for mentoring. Just plug in your zip code in the little box here and you will find opportunities to mentor a child in your area. If you're nervous or aren't sure what you would do with a child, this site gives you a LOT of resources. Something to explore for sure!