I went with Inca Floats (out of Emeryville, California, and I think they have a website) in '98. A friend of mine had researched many tour groups and raved about them, and I concur. Among other things, they use their OWN guides instead of whomever is assigned by the government, and our guy was a Ph.D. with expertise in geology, biology, and astronomy. The groups were also small, which is CRUCIAL in the Galapagos. My only gripe against them is that they don't take credit cards.