Ok, so I am a nerd. What can I say? I love books. Books are my most profound teachers. A book can unlock a practical problem or provide a hint to something your unconscious is trying to solve.
Reading also uses the whole brain (symbols turn into words, words turn into meaning, etc). In short, I love books. I am always thankful to learn something new. There is nothing like the feeling of Aha!

The Language Instinct
by Stephen Pinker

The Hero with a Thousand Faces
by Joseph Campbell

Guns, Germs, and Steel: The Fate of Human Societies
by Jared Diamond

Archetypes and The Collective Unconscious
by Carl G. Jung

Maslow on Management
by Abraham H. Maslow
5 books that deliver an abundance of Aha! moments:
by Stephen Pinker
by Joseph Campbell
by Jared Diamond
by Carl G. Jung
by Abraham H. Maslow