Rather than looking for work on-site, I would try working remotely. You'll have a much bigger market to sell your skills to. Can't really help you as far as specific sites or employers go, but it seems to be fairly common.
By saying that you'll work for room and board, you're not establishing the best positioning. You're much better off separating your consulting practice from your living arrangements. Establish yourself as a credible and professional developer rather than one who "will work for food".
I've been traveling nearly continuously for the last 3 years, funded by a successful consulting practice. If you have the skills, there are plenty of well-paying offsite consulting gigs to be found. Of course, having "the skills" also means knowing how to market yourself, negotiate, and land and keep clients.
You may want to consider the possibilities of geo-arbitrage, having clients in higher cost-of-living countries, and spending some of your time in lower cost-of-living countries.
Travel Well.
I travel and work remotely. Work hard at finding a good gig at home/your native country and plan ahead - you can move and work almost anywhere in the world. Beware of the small unconsidered things: for example where I was living in Mexico we would lose power on a regular basis, for a period of hours or days. So, no working at home that day but I could get out of the house and work in an internet cafe. These small pieces of knowledge - being prepared for the unexpected - have saved my ass when travelling.
Not sure how to help you with the job stuff, but this e-book will help you save a lot of money travelling. I read about it on nerdfitness.com and it supposedly will help you drastically cut travel costs.
I've been using oDesk to do some remote work. You can definitely scale remote working to where you have enough money to travel.
Most places I've been always have an internet connection in easy reach.
I would _love_ to be able to do this myself. Extensive travelling is actually probably one of my highest goals in life and being able to support myself as a developer through that would be _so_ awesome. Totally down for helping you build this network if you're lookin' for it and there's interest.
You're heading in the right direction, but I'd actually recommend a different approach.
Try working for a few places over the next couple years and build yourself a reputation as being good at what you do. Get some products shipped that you can point to. Build some side project stuff that you're proud of. Basically, get yourself employable.
Then go off and start traveling with the laptop.
You see, when you first start out, you're unlikely to find many people willing to pay you $75/hr to work from a Hammock in Laos. Who is this kid and what is he smoking?
But if you're the kid that built X. You know, _X_! And he's available to work for us. I know, he has some silly demands about time off and we won't be able to get him on site, but hey, he built __X___!!! There's no doubt he'll deliver.
Anyway, that's my 2 cents, having built X myself at your age and milked it into 10 years of living on beaches with a laptop. It's all good out here, so I definitely hope to see you on the road some day.
But before you do, I'd recommend putting in the groundwork to make sure you can pull it off.