Understanding Comics by Scott McCloud; HarperCollins Publishers — The definitive work on the structural and conceptual underpinnings of comic books. No other book discusses the medium in such depth, in such an entertaining format.
Drawing Words & Writing Pictures and Mastering Comics by Jessica Abel and Matt Madden; First Second — The next generation of how-to books, with an accompanying website chock full of projects and info.
Comics & Sequential Art by Will Eisner; Poorhouse Press — Eisner’s film noir-influenced drawing style and compositions in The Spirit influenced countless aspiring artists. His classic exploration of comics storytelling is geared toward illustrators, but is highly recommended for writers too.
99 Ways to Tell a Story: Exercises in Style by Matt Madden; Chamberlain Bros. — The title says it all. An inspiring application of different storytelling approaches to the same one-page sequence.
Alan Moore’s Writing for Comics by Alan Moore; Avatar Press — A short collection of essays about writing comics, by one of the medium’s most respected, talented, and quirky writers.
Write Now! magazine, edited by Danny Fingeroth; TwoMorrows Publishing — A quarterly magazine about comics writing, featuring how-to articles, interviews, and script samples.
Alternative Scriptwriting by Ken Dancyger & Jeff Rush; 1995, Focal Press/Butterworth-Heinemann — A wide-ranging examination of story structures, genres, character arcs, themes, irony, symbolism, and more, using many cinematic examples. Concise and accessible.
Making a Winning Short by Edmond Levy; 1994, Henry Holt & Co. — Contains a useful guide to developing character profiles.
The Comic Book Script Archive — Sample scripts donated by professional writers.
Jessica Abel and Matt Madden both have great educational info and links to other resources on their individual sites as well as their Drawing Words & Writing Pictures site.
Jim Zub posted a series of blog articles about comic book writing and the comics business.
Joel Fagin wrote a series of tutorials about webcomics.
The Center for Cartoon Studies — School offering workshops and an MFA in creating comic books. The info/how-to brochure alone is worth a look.
Other organizations offering courses and degrees in comics include the Kubert School, the School of Visual Arts, Savannah College of Art & Design, Portland State University, the Independent Publishing Resource Center, Meltdown Comics, and quite possibly a school or library near you.
FOR EDUCATORS AND LIBRARIANS
The Comic Book Legal Defense Fund (CBLDF) — Nonprofit organization dedicated to free speech and comics as literacy and educational resources.
Scholastic — The venerable educational publisher has joined the digital/visual age, offering a "Guide to Using Graphic Novels with Children and Teens" and a wealth of other lesson plans, reading lists, etc.
FOR YOUNG READERS AND CREATORS
For budding creators, the Adventures in Cartooning series is an inventive, inspiring, interactive exploration of comic book techniques, told in narrative form.
Scholastic's Graphix line not only publishes wonderful graphic novels such as Bone and Amulet, but also has an online "comic builder" feature and drawing tips!
Happily, after a long dearth, these days there's an ever-changing assortment of comics suitable for a diverse range of young readers. Below are a few lists of recommended reading, and I'll expand this section in future. Meantime, I encourage you to Google it yourself, or ask your friendly local comics retailer or librarian!