Trader Tiki offers an invaluable roundup of some old cocktail books that have passed into the public domain. With links to full-text PDF versions, even. What a great resource to peruse.
Not-so-incidentally, one of those books is the grandaddy of them all: Jerry Thomas' 1862 magnum opus How To Mix Drinks: Or,The Bon-Vivant's Companion, the first bartending book ever published. (I'd be remiss if I didn't note that the book has been available on The Art of Drink as a painstakingly transcribed online version.)
And incidentally, as every cocktail geek knows, a biography of Thomas by David Wondrich came out not too long ago. (It looks great, but I confess that I'm a bad cocktail geek and haven't yet read it, though it is on my mammoth to-read pile.) And a hot tip I just received from an unimpeachable source: Wondrich will be appearing -- and making cocktails -- on NBC's "Late Night with Conan O'Brien" tomorrow (Friday) night. I look forward to checking it out.