1. Languages:
fourhourworkweek.com
2. Work at a farm:
wwoof.com
workingoverseas.com
3. Find information
jiwire.com
4. For an accommodation
homeexchange.com
hospitalityclub.org
couchsurfing.com
globalfreeloaders.com
5. For flight ticket
orbitz.com
priceline.com
cfares.com
i800flyeurope.com
easyjet.com
vitualtourist.com