Biology student in need of reading recommendations

I want to get a good understanding of biology as a whole. I'm planning on teaching biology at some point in the future, whether it's my career or just a hobby. I'll have some time this winter to catch up on my reading, and would like some recommendations.

I'm working on a BS currently, so I'm still scratching the surface. I've read Sagan's Shadows of Forgotten Ancestors and really enjoyed it. I've ordered a few Stephen Jay Gould titles and some Dawkins, but would like to hear some of your favorites.

I'm particularly interested in evolution (yeah, broad, I know), mycology, and beginning to get interested in microbiology, but like I said, I'm interested in every aspect of the field. Searching for "biology" in amazon's search brings back mostly textbooks. I have plenty of those already.

Edit: Wow, so many replies. I've now got a list that might last me a lifetime. This is exactly what I was looking for, and I'm very thankful/surprised that everyone took the time to comment. Thanks for your help, every last one of you.