I always enjoyed Stephen Jay Gould's collection of essays on natural history and would like to add a few to the already great list posted here.
Bully for Brontosaurus
Eight Little Piggies
Dinosaur in a Haystack
Hen's Teeth and Horses' Toes
Time's Arrow - Time's Cycle was pretty good, too.
Another author I enjoy is William H. Calvin:
How the Shaman Stole the Moon
Ice Age Climates and the Evolution of Intelligence
This is stuff from the 90ies, but it should still be very readable.