Books

Now, the Internet is a wonderful thing, at least if you are making money off it, but what do you do when the lights go out? Why, light the oil lamp and head for the bookshelf, of course!
The Rigging Loft library includes a few classics, some of which I've carried around since my days on the Chase.
My first couple of reference books included Hervey Garret Smith's The Arts of the Sailor, and that seabag standard, Knight's Modern Seamanship.
As a core of your own bookshelf, I can't recommend The Arts of the Sailor highly enough.