General resources for New Yorker cartoons, art, and cartoonists online
The Cartoon Bank
The New Yorker’s Cartoon Caption Contest
The New Yorker’s Cartoonist of the Month blog
Skating cartoons from the magazine
Chris Wheeler’s gallery of cartoons and cartoonists

Cartoon collections and other books of note
They Moved My Bowl: Dog Cartoons by New Yorker Cartoonist Charles Barsotti (Little, Brown)
Funny Ladies: The New Yorker’s Greatest Women Cartoonists And Their Cartoons, by Liza Donnelly (Prometheus Books)
Sex and Sensibility: Ten Women Examine the Lunacy of Modern Love…in 200 Cartoons, edited by Liza Donnelly (Twelve)
Last Laughs: Cartoons About Aging, Retirement…and the Great Beyond, edited by Mort Gerberg (Scribner)
Mixed Company: Cartoons by Michael Maslin (Fireside)

Cartoonists
Charles Addams [Comiclopedia]
Charles Barsotti
Harry Bliss
George Booth [Wikipedia]
Tom Cheney [Comiclopedia]
Sam Cobean
Frank Cotham
Michael Crawford
Leo Cullum [Urban Dog]
C. Covert Darbyshire
Drew Dernavich
Eldon Dedini
Matthew Diffee (plus my review of a Diffee Rejection Show appearance)
Liza Donnelly
Emily Flake
Mort Gerberg
Sid Harris
Marshall Hopkins
Carolita Johnson, a.k.a. newyorkette
B. Kliban
Eric Lewis, cartoonist and sculptor of the ingenious and beautiful Garbage Flowers
Marisa Acocella Marchetto, author of the highly recommended graphic memoir Cancer Vixen: A True Story
Jerry Marcus
Paul Noth
Jason Polan
What to Wear This Very Second [Emily Richards]
Elwood Smith
Mick Stevens [website]
I Really Should Be Drawing [Mick Stevens’s blog]
P.C. Vey
Rowland B. Wilson

Covers and cover artists
Cover Browser [Incredibly rich collection of New Yorker covers]
Covering The New Yorker [Introduction by Françoise Mouly]
45 New Yorker covers
Some ’30s covers
Arthur Getz
Ana Juan [Emdashes on Ana Juan’s cover “Homage,” March 29, 2010]
Jacques de Loustal
Max
Peter De Sève
Gretchen Dow Simpson
Edward Sorel
Art Spiegelman
Adrian Tomine

Photographers
Mary Ellen Mark
Sylvia Plachy

Illustrators and other artists associated with the magazine
Roxanna Bikadoroff
Steve Brodner
Erik T. Johnson
Edel Rodriguez
Gerald Scarfe
Reinhard Schleining
R. Sikoryak
Mark Ulriksen

Related organizations
Thurber House

Old issues and the archive
The debut issue: an eBay auction

Articles, papers, interviews, websites, &c. about art in The New Yorker
Paper: “Eustace Tilley Sees the Thirties Through a Glass Monocle, Lightly: New Yorker Cartoonists and the Depression Years,” by Eric Solomon (San Francisco State University)
Review: Funny Ladies: The New Yorker’s Greatest Women Cartoonists and Their Cartoons, by Liza Donnelly, and The Comic Worlds of Peter Arno, William Steig, Charles Addams and Saul Steinberg, by Iain Topliss; reviewed by Emily Gordon (Newsday)

This list is, of course, incomplete; these categorizations are subjective (cover artists also do cartoons, and so on), and likely to change. Please email me your suggested additions or corrections, and if you are an author or publisher, please let me know if your book should be included here. Thanks!