Worldpackers
Worldpackers is a collaborative platform that connects travelers with their hosts around the world (170 countries) where they can travel using their skills in exchange for accommodation.
There are hostels, inns, NGOs, communities and ecological projects to which you can offer your help and in return receive free accommodation, meals and other benefits.
How you can apply
1. You must become a verified member (there is an annual membership fee of $49);
2. Candidates for positions with different hosts;
3. You talk to the hosts and you can ask any question;
4. You get pre-approved if the host likes your profile;
5. You confirm the trip.
More information here.