Graymouser's Guide to Anime Art Terminology - A full survey of the types of sketch, background, and cel art available, along with common problems encountered. Well illustrated with clear, engaging commentary. Even experienced collectors will learn something here.
"Anime Job Titles" - Lucid overview of the Japanese animation process by a former employee. Invaluable for identifying the various levels of sketches.
Inuyasha Director Guide - Useful guide to the various animation directors who contributed to this series, with interesting comparative notes at the end of the list.
The Obakemono Project - Great introduction to the Japanese folklore of monsters in all sorts and shapes.
CCSvsCC Episode 1 - Shot-by-shot overview of the opening episode; essential for locating cels and putting them into context. The entire site is well designed and well worth exploring.
The Insatiable Critic - Nice movie/DVD review site with a quirky point of view and a keen interest in new (and old) animated movies and TV series.
Kamidake - Well-designed animation art gallery with especially good CCS/MKR/TnN holdings.
Graymouser's Cel Gallery - Pretty self-designed animation art gallery, with strong CCS holdings.
Kero's Corner - A delightful collection focused on Kero-chan and Kerberos
Mon petit loup Syaoran - A Japanese collector's artistic gallery focused on Li Syaoran