(Matador Network) — The chance to give something back, an opportunity to share your skills and knowledge, to meet other travelers or simply to meet the locals...

There are many reasons to volunteer while you're traveling and there are literally thousands of charities and organizations that look for help from passing travelers.

Many ask for donations or fees to cover costs and others operate as for-profit businesses, but the list below includes only those that cost little or nothing to get involved with and help out:

Board and lodging is offered in exchange for a day's work on the farm. Stays available from one week to many years, and with thousands of hosts available in 53 countries there's an opportunity suitable for everyone.

2. Turtle Teams, Worldwide

A generic name for the thousands of small groups that help threatened sea turtles. Most groups are based at one or two nesting beaches — which are typically at risk from over-exploitation — and appreciate help for even just one night.

Search for groups at the local tourist office close to any tropical beach and help a species come off the endangered list. More information can be found at these larger organizations: www.seaturtles.org and www.cccturtle.org

3. Conservation Volunteers , Australia and New Zealand

Through various short-term projects in Australia, New Zealand, and a few international locations, you'll work in teams to protect habitats and promote ecotourism.

A small fee (usually around AUS$100 for a week) is usually required to participate, but covers all food and lodging. UK-based BTCV (British Trust for Conservation Volunteers) has similar opportunities.

Teach English in one of the world's most impoverished countries. Placements are at schools or universities, but many volunteers help with community projects in additional to their teaching.

Volunteers must pay for their airfare but all other costs are covered, and a small monthly stipend is provided.

At over 2,000 miles long, the Appalachian Trail is the classic long trail in the Eastern US and home to almost 2,000 endangered or threatened species.

Volunteers help with trail building and maintenance in return for food and (usually very basic) accommodation.

One of Europe's most popular walking holiday operators is searching for volunteers to guide their treks. Leaders are provided with accommodation, meals, and the chance to explore Europe in return for sharing their passion and knowledge with the groups they accompany.

A website that lists worldwide hosts who are looking for an extra pair of hands, whether it be in their farm or garden, working in schools or on religious projects, building houses or community centers, or simply helping a family take the kids to school.

A small membership fee is required to access host details, but board and lodging is provided in exchange for your work.

A unique chance to live and work in another country. Participate in a variety of projects, from healthcare and the environment to business development.

A commitment of 27 months to the placement is required, but for those who are willing, this is a life-changing position. Open only to U.S. residents, but similar projects are available for other nationals with VSO.

From healthcare and economic development to assisting after natural disasters, the UN offers positions for those who are dedicated to making a difference abroad.

While many positions are open only to experienced professionals, the UN has links to hundreds of international NGOs and QANGOs that are looking for help in similar fields on a less formal basis.

An area that is rarely out of the news, Israel is a land of tight communities but complicated politics.

Being a volunteer here gives you the opportunity to experience this region firsthand while living as part of a socialist community where everything is provided. The region also serves as a good base from which to explore the Middle East and North Africa.