Santa Fe is a small island, but has an interesting cactus forest and range of birds. As it's close to Santa Cruz, it can get quite a few people on day trips.
See the Galapagos wildlife page for information on the flora and fauna of the islands.
A wet landing on a '''sea lion''' covered beach leads to two different trails.
One of the trails leads through an '''Opuntia cactus''' forest where you can see '''Yellow Warblers''', '''Galapagos Mockingbirds''', '''Galapagos Doves''', '''Lava Lizards''' and of course some '''Darwin Finches'''.
Apparently there is good snorkeling off Santa Fe.