I have a close friend in OT right now (I'm in PT, just started). It seems like his course work focuses more on functional aspects of the human body, or "occupation." They get the same basics of anatomy, neuroanatomy that PT's get, but the rest of their courses seem to analyze daily tasks. What goes into the action of writing, typing, lifting objects, etc.
So, in a clinical setting (this is more so what I've observed in various places I've worked in) it seems like OT's are more concerned with how do we get this person brushing their teeth, putting their socks on, taking care of their home etc. etc. now that they are injured. Whereas PT's work on the biomechanics of the body to get them BACK into doing those things by themselves by assisting with healing of the injury (strengthening, stretching, manipulations, etc).