I would be remiss if I didn't include my photography professor from Oberlin College, Pipo Nguyen-duy, as one of the most truly inspirational photographers of my life. He was just awarded a 2011 Guggenheim Fellowship. Go Pipo!
Whenever I'm feeling "meh" about my own work, I try and think "What would Pipo do?". He always helped us to explore our ideas to their fullest and threw us into challenging projects and techniques with an air of mischief and fun -- always with the expectation that we would push ourselves to the limit both conceptually and aesthetically.