with a working holiday visa you can work in the country you're visiting, but with the main focus being travel. not every country has ties with other countries, so to see in which countries you're able to get this type of visa go here.
there are plenty of websites where you can look for international job opportunities, such as seek.com or the endless temp agencies around the world. in my experience it's really hard to get a job as a backpacker, unless you have certain skills the country where you're going needs. you can basically pack your stuff and leave whenever you feel like it, so some companies are reluctant to hire travellers, don't take it personally ;) also don't expect to make a lot of money, your work is supposed to get you through travelling not finance a new house or car. there are many exceptions of course, but you just have to be lucky i guess.
what i do when i get to a new place is print out my cv and just go around town asking for work, this way you get to show your face and people or more likely to give you advice on where to find jobs and who might be looking for help. some hostels offer help in finding work, but in my experience it's better to just do it yourself.
