Summer camp I worked at had international staff through one of the above organziations.... most enjoyed the summer. Our sessions were 9 weeks long and staff bunked with campers so really 24/7 responsibility. They got off every 10 days, maybe one evening/wk. Luckly, I lived in the infirmary with my kids. Some years I had helper, others another RN. BEST part of summer camp was meeting/treating international staff.
Get that pen out and start writing! Here's link to American Camping Association:
http://www.acacamps.org/jobs/
International Staff