Volunteer on a yacht
You don't have to be an expert or even have any experience to be part of a sailing crew. Duties and arrangements vary, of course, but usually you are getting free board and of course transport, while learning a brand new skill. Sometimes, experienced skippers get paid to navigate other people's yachts from one place to another - nice work if you can get it, and a good goal to aim for.
Airbnb is, I think, one of the greatest uses of the internet. Basically, people can list their spare rooms/entire homes/treehouses for rent to travellers. Like Blablacar, profiles are linked to social profiles, so you know you're not staying in the home of a sociopath. Also, if you have a space it's an incredible way to make a bit of cash to fund travels. I'm currently staying with my boyfriend's parents as we've rented our room out to two lovely Italian boys. It's a pretty nice way to get some extra cash, if you can swing it. If you're the renter, it's guaranteed to be cheaper than a hotel and nicer than a hostel.
If you're not already a member of Airbnb, I'd appreciate if you could click this link when you do it - I get store credit for the referral!
Another social network of travellers and hosts, couchsurfing is pretty ace if you are happy to take what you can get. The friend who hitched from France to Norway is a very keen couchsurfer (she couchsurfed through India - again, not something I would have done), and she swears by it. Her safety tip is to read reviews and read between the lines: there could be a warning that the host is potentially a bit dodgy.
I'm not counting the kind of volunteer experience where you have to pay loads of money to spend three days in Africa - that is noble but it is not cheap. On the other hand, there are several networks where you can find yourself board and accommodation in exchange for a few hours a day work. Jobs might range from restoring a C18th French chateau to cooking for a family of 10 on their sustainable smallholding in the Rocky Mountains. You never know.
There are certain strata of society who pay a lot of good money to fly tutors or child minders to exciting destinations. You have to know what you're doing and they usually require a degree from a good university, but it's food, accommmodation, travel AND pay; if you think you'd fit the bill, it's definitely worth looking into.
From what I hear, people younger than retirement age sometimes have a hard time securing house-sitting gigs. Still, there are people who seem to have cracked the formula. Here's a couple who seem to have been doing alright:
A friend of mine told me she hitchhiked from Paris to Norway last year. This is not something I would ever dream of doing, because everything I've been taught about hitchhiking is that you end up murdered in the woods. However, I've come across a pretty awesome carshare website that links to your Facebook profile and has user-reviews, so that you can be assured that the driver is not a serial killer. If you're a woman, you can also request women-only trips for extra peace of mind, which I think is a nice touch. The price of the trip is fixed beforehand, and you can even select the option for whether you want to have a quiet journey or a chatty one.
Despite having the pretty lame name of "Willing Workers On Organic Farms[-ing]", it's a pretty cool idea - basically a network of organic farms that accept travellers to exchange work for food and accommodation. Another friend worked for a while on a Japanese farm. One time, she and her friend had to pick snails off the crops and put them in sack, counting the snails as she went - there were thousands. She realises in retrospect that the counting was probably a joke but the language barrier made it difficult to detect the hilarity. But the best part was that they left the sacks full of snails in the back of the truck - only to come out the next morning to discover the snails had escaped the sacks through the night and were swarming the entire truck.
Everyone knows someone who knows someone who can get you a sweet deal or put you up, especially if you're not too far off the beaten track. Put out a Facebook call-out and ask if anyone needs a house-sitter, pet-sitter or a subletter, if anyone is driving somewhere and would like company and a contribution towards petrol costs. If you're staying at a hostel, ask if there are any jobs going in exchange for accommodation. There's a network for finding friends of friends, too: