Looking to do a gap year? There is a lot on offer, to help you work your way through this there are some useful websites that can give you information on making your decision.
One thing to consider, when looking at volunteering is whether the company is ethical, and makes a genuine difference to the community it's placing you in. Not all "volunteer" organisations are ethical and genuine. There are a number of charities that do offer Gap Years, and are committed to volunteering ethics. Gap advice has a section on ethical considerations to think about when thinking about your Gap Year.
VSO ICS is a government funded programm run by Voluntary service overseas an international volunteering charity (18-25)
Lattitude Global Volunteering is an international youth development charity (17-25 year olds)
BUNAC Working Adventures Worldwide provides ethical, low-cost volunteering programmes in Africa, Asia and the Americas
Community Service Volunteers (CSV) olffers a range of volunteering projects in the UK. They offer gap year placements from 6 months to a year (including free accomodation and day to day expenses). As well as short term opportunities working on historic buildings or doing environmental work.