There are several volunteer organizations, companies, and individuals all over the word that are willing to provide you housing and food in exchange for work.  I have complied some resources for you below and encourage you to check them out if you are planning on traveling on a low-budget:

wwoof.org – This website helps connect volunteers with organic farmers lloking for help all over the world.

helpx.net – This website is loaded with Farmers, Rachers, Hostel Owners, Bed & Breakfast owners, even boat owners willing to provide accomodation in exchange for volunteer work.  You do have to pay a small fee to become a member on this site, but with options in nearly every country I think it is well worth it.

peacecorps.org - If you are willing to donate 27 months of your life to volunteer work, the Peace Corps may be a great option for you.  They also have many benefits such as student loan deferment and transition money when you get out.  The only catch… application waiting times can be up to a year long.

workingcouples.com –  Looking to travel with a significant other?  Check out this website.  There are not a ton of overseas options but it’s free and easy to use.

aupair-world.net – Be an Aupair for a family overseas and get paid!  Free to join.

caretaker.org - Some people are just looking for house-sitters and many of them post here.  You have to pay to be a member, but there are several positings all over the world.

idealist.org – If you are interested in volunteering and working in the non-profit sector create a profile on this website.  There are thousands of job/volunteer postings all over the world and it’s free to join.

If you are not planning on volunteering and just looking for a cheap place to stay, I highly recommend couchsurfing.org.