The camera is on the end of the arm at the bottom left in [1]. By comparing that to this picture you can see where part of the arm is in the self-portrait, above and to the left of the front-most wheel. The third-person perspective in the self-portrait comes about because the robot arm will always move out of the way of any photo that the camera is taking.

[1] http://en.wikipedia.org/wiki/File:PIA15279_3rovers-stand_D20...