Hey, it's what I went to school for! Well, sort of, but it ended up being a large part of my education. Paper arts is one of those craft categories where you can pick a project that's either really, really cheap - or really, really expensive. The best examples would probably be simple card crafting on the cheap end, and bookmaking on the "wait until your next couple of paychecks" end, but both are fun and rewarding. For a paper geek like me, it gets my heart racing. Here are some supply sites and general resources on the web I find to be really helpful. I can't offer you any tutorials on the web because I still haven't found any that I like which illustrate and explain it well for beginners; I've included some good binding books in place of any web tutorials.
Suppliers - Bookbinding
Talas: they have everything under the sun for the book arts and are the first company I went to in college for more advanced supplies. They've got a great selection of book cloth to choose from (sample swatch books available for purchase!), and their book selection is definitely worth checking out (a number of them I either own or have read).
Hollander's: I'd heard about these guys recently. Their retail storefront is located in Ann Arbor, Michigan, but they also sell their supplies online. If you're a beginner, they have large variety of text blocks already sewn and finished so you don't have to worry about the sometimes frustrating steps of gluing your signatures. All you have to do is add your endpapers and attach to your covers!
Suppliers - General Paper Crafts
Paper Mojo: I could stare at their Contemporary Prints section all day. They've got all sorts of awesome papers to choose from, from patterned to lace to tissue.
Martha Stewart Crafts: whatever, I'm a sucker. Really beautiful ribbon, paper, punches, embellishments, et cetera, et cetera, et cetera.
Kraft Outlet: I love brown kraft paper. I'm not sure what it is about it, but it's awesome. Kraft Outlet has a whole bunch of nifty things for packaging, stationery and other various paper-based projects in sweet, sweet kraft.
Creative Paper Crafts: I found some pretty cute rubber stamps here. They've got supplies for a variety of crafting techniques including origami, embossing, and quilling, as well as scrapbooking supplies.
Resources and Information - Letterpress
Don Black's First Press Suggestions: want to get into letterpress but you don't know which machine to start with? Here's a good page to get your started.
Briarpress: the letterpress printer's haven. Whether printing is new to you or you're been doing it for a while, there's something for everyone, including classifieds (need a printer?), help forums, and workshop / class announcements.
David Rose's Introduction to Letterpress Printing: really resource for information about the history of letterpress, printing manuals, equipment, and supplies.
Resources and Information - General Paper Crafts
Martha Stewart Crafts Projects: if you're doing paper crafts, might as well go the patron saint of all things (somewhat) crafty, Martha. There are actually a bunch of really cute projects here that can really inspire new ideas and don't necessarily utilize her product. It's well explained and illustrated, too - heck, I used to design and create place cards for a living (worked at an invitation store), but I'm not sure I could have explained the process of pop up place cards better than the way it's described in the Themed Bird Party place card instructions!
Books - Book Binding
Making Books by Hand by Mary McCarthy: I bought this book back in school during my sophomore year, when I was first getting started in bookbinding. It was a really helpful reference on alternative binds or little things I could do while constructing my book to make it special. I'd definitely say it was a worthwhile purchase, especially for a beginner, because of its clear photos and easy to follow, step-by-step instructions.
The Encyclopedia of Papermaking and Bookbinding by Heidi Reimer-Epp: this book really has a bit of everything in the process of making a finished book, from the papermaking process to several varieties of binding. It's well illustrated and explained, so anyone of any skill level in either area can easily pick up the crafts.