I've seen the green flash three times, and two of them were while I was on a boat in the Galapagos. I thought some of you out there (specifically, the other Eric) might be interested in these photos that I managed to snap. For a good explanation of why the green flash occurs, check out Andrew T. Young's page.
green flash, clearly visible. i think it's a mock-mirage flash.
not as obvious, but it was green to the eye.