There are so many books and web sites that focus on different aspects of puppetry that I could never list them all. What I have collected below are ones that I've personally found useful or interesting, and I hope that you will, too.
Sagecraft's 'The Puppetry Homepage' - You'll find links to a ton of other puppetry resources on this website.
The Center for Puppetry Arts - A permanent puppet theater right here in Atlanta. Be sure to check it out if you have any kind of interest in puppetry.
The Atlanta Puppetry Guild - Atlanta's local association of puppeteers and puppet enthusiasts.
The Puppeteers of America - A national puppetry organization that is also the parent organization of the Atlanta Puppetry Guild.
Axtell Expressions - Need your own puppets? This is the place to go if you want to buy high-quality professional puppet characters.
Animal Makers - Need your own high-end puppets? Check this group out for TV and movie-quality realistic animal puppets.
Mailing Lists / Forums
Puptcrit - A mailing list dedicated to puppetry and related topics.
Puppet Hub - A global network for professionals, amateurs, and people who just like puppets.
Puppets and Stuff - A Community on the Web for Puppeteers.
Making Puppets Come Alive: Larry Engler and Carol Fijan (1973)
The Complete Book of Puppetry: George Latshaw (1978)
The Foam Book: Drew Allison and Donald Devet (1997)
Puppets and Puppet Theatre: David Currell (1999)