Every sailor should have a copy of
"The Friendly Stars"
an elegantly simple introduction to naked-eye astronomy and the 21 brightest stars visible from the northern hemisphere (sorry, antipodeans, I don't know a corresponding title for your skies. If you do, please post it.) These 21 stars are your street signs in the sky. You can start using the book right away, and work your way around the sky over the course of the year. No instruments required, just a clear sky and the good old Mark I eyeball. This the best introductory-astronomy book I know.
A couple of useful astronomy sites:
shows you what you can see in your patch of sky.
"Follow the arc to Arcturus, then speed on to Spica":