There is a facebook page for photographers, models and make up artists that like-minded people can put a shout out for collaborations onto. I used it to put my Pre-Raphaelite shoot together in March.
Jemma-Jane, or JJ for short, put out a shout out for photographers for a fitness shoot she was putting together. Professing an allergy to all forms of physical activity I did not feel comfortable offering to be primary photographer on such an assignment, however I did offer to be a second / behind the scenes shooter.
Here is what I got: