You can find summer camps/intensive programs advertised on the same employment forums as full time work.
There seems to be less work advertised each year, so the selection may not be as large as it used to be.
You should expect long hours and a hectic schedule. You most likely will not be reimbursed for your travel.
Your stint should include housing, meals and some wages (more about that later).
Camps range in length from usually ten to twenty days. It would be rare, in my experience, to find a camp that ran all summer.
You will not find wages to be very high. There are many organizations where young people pay for the experience to volunteer for summer teaching experience at for profit institutions. Many camps pay only a modest stipend in addition to room and board. Other schools may pay more, 60 -100 RMB per hour seems to be the usual range.
Summer camps will usually offer little, if any, opportunities for sight-seeing or free time to explore locally. It is a busy time.
I don't have any specific organizations that I am familiar with enough to recommend or suggest avoiding.