This is probably the largest online community for finding English teaching jobs all over the world. There is an entire section dedicated to China as China has more English teaching positions than any other country. Here you will be able to look at job postings and get in touch with the recruiters at the school or agency that posted the position.
It should be noted that many of these institutions can be shady, and stories of foreigners landing in China for very little pay, in a backwater town that they did not want to be in are common. I recommend either liaising with the university or school directly, or even better, finding a reputible institution or agency in your home country that has connections with schools in China.
This website is like Dave’s ESL café, but strictly for foreigners looking to teach at universities and training centers in China. I have friends who have had good success with this website and the university I taught at also posts positions here.
Confucius Institutes are located all over the world and are places of learning set up by the Chinese government. The one above is for the institute located at the University of Minnesota. You will probably get a lot of help in your quest to find an English teaching position in China here, or even a non-teaching position.
Job and Volunteer Fairs
Although I put this last, this is probably the best option and is how I found the group that sent me to China for the first time. Some universities will have job or volunteer fairs, which have recruiters from schools and teaching programs abroad in China.
Contact people in your network and at your alma mater to see if there are any ties to teaching English in China. You will probably not have to look far. A Google search will also turn up many such institutions.