John on LIK's hook. Someday I'm going to get that other email so I can do it myself.Best place to get started is certainly with people who play and make instruments, as suggested by others above. If you get into making instruments like the P-squeeks, you may eventually want to look at some other kinds of similar projects.
"The Amateur Wind Instrument Maker" by Trevor Robinson, University of Massachusetts Press, 1973 & 1980, ISBN 0-87023-312-2 (1980 edition), about $18.00 & probably available from Barnes or Borders .coms: has some detailed plans for a variety of fipple flutes, recorders, etc. You might find a variety of instruments here that would be fun to build. This book has been cited frequently by a number of sources, and may be available in a local public or university library for you to look at. It's only about 100 pages, but has some good stuff – including a short list of other useful references.
Almost any published "work" on instrument design eventually mentions "Acoustical Aspects of Woodwind Instruments" by C. J. Nederveen. I spent about 2 yrs looking for this one, because so many people recommended it, and it has been re-published (1998) by Northern Illinois University Press, ISBN 0-87580-577-9. I got my copy about a year ago, by special ordering it (for $28). Unless you are mathematically inclined, I'd say don't bother – at least until you have tried out what you can find elsewhere – or hit the libraries again. It's a good book, but you probably don't need it for what I infer as your interest.
Dover books (reprints) also have a number of historicly interesting technical stuff that you might want to look at (Helmholtz, Jeans, etc.) later if you get obsessed. Best bet is to make a hole in a long hunk of wood, bust through some side holes, and play with it -- after you get the fipple angle and spacing about right.
And have fun!!!
John in Kansas.