Most Photographers use Apple Aperture which is a Powerful photo editing and management. I also use this especially when I have mini Photo Shoots where I can "tether" my cam on to Aperture and have the photos I take go directly to my computer.
http://www.apple.com/aperture/whatisaperture/
But im sure there is other software that allows you to Tether your camera to your computer i remember that Canon has an app that comes with its P&S cameras even though you cant with them which i thought was pretty pointless.