Nicaragua has a very developed volunteer culture traceable to the influx of 'Sandalistas' (young foreign volunteers) during the revolution. Many hostels and Spanish schools maintain lists of organizations or check out Volunteer South America and Go Abroad.
Following are some organizations that accept foreign volunteers.
Nicaragua is one of the poorest countries in the hemisphere, with almost 50% of its adults unemployed or underemployed. Thus, finding a job in Nicaragua is difficult and taking one that a Nicaraguan could be doing is probably just plain wrong. Backpacker-oriented businesses may offer you under-the-table employment, usually in exchange for room and board, but this is mostly about extending your vacation. If you’re a serious, qualified English teacher, you may be able to find a job in an international school or private-language center.
If you’ve ever thought about living and working in Nicaragua, then why not teach English as a foreign language (TEFL)? It could be the key to funding your travels and experiencing new cultures in a totally new way. You don’t need teaching experience or even the ability to speak the local language – although you might learn it while you’re out there.