Making money on the move is not easy especially if you are not planning to settle down for long period of time, as you would need to in order to teach english. The main hassle is the working visa.
Another option is working as a free lance journalist or photographer. The best money is by finding a magazine at home (or in any western country) but it is very difficult unless you have a degree in journalism and/or photography, or some experience with some work to show, or a good connection in a magazine - and even though it is not easy. The alternative for that is writting for a local magazine in the country you're in, they sometimes are eager to find native english speakers to write artcicles for them. Go to some local book shops, and look in the magazine section, find magazine and papers that inspire you and write down the editorial contact, give them a call, or - even better - stop by. I would recommend having some work to show them. Also try airline magazines for local airlines, they pay decent money ($50 to $250 per article depending on the number of words, if you provide pictures with it or not, and of course the airline). The advantage of that if once you found a magazine and they like your work, you can work for them. This is how Heinz Stuck earned a large part of his money while he was traveling (not sure if he still does it).
Australia, NZ and some western country are good places to pick fruits. It's easier (easier not easy) to get a working visa for Oz and NZ, but very difficult in western European countries and the US.
You can make some serious money in the fishing job indutry in Alaska. I met someone who used to go there every summer (I think it's high season for salmon) and made $1200 a week! Try to google it if you're interested.
Good luck, and let us know how it goes!