There are several significant online resources that can enhance the study of animal development. Although there are many that could be cited, here are a few of my favorites. My apologies if your site isn't here; this idiosyncratic list contains site mostly selected because they have large numbers of great movies or image montages...

Books and Instructional CDs
Scott Gilbert's Developmental Biology, 6th edition, at NCBI: the current edition is the 7th, but this us a great resource, including most line art.

Scott Gilbert's Developmental Biology, 7th edition site (Sinauer): site linked to the current edition of Scott's book.

Vade Mecum: site that supplements Tyler and Kozlowski's Vade Mecum CD and Mary Tyler's lab manual. Staging series, interactive games, and more.

Fred Wilt and Sarah Hake's Principles of Developmental Biology student web site: provides links by chapter to various topics in developmental biology.

Gastrulation: From Cells to Embryos (Claudio Stern, editor): Online supplement to the book from Cold Spring Harbor. Many images, and several chapters have great time lapse movies.

Course web sites
Mark Hill's embryology site (University of New South Wales): Contains links to many movies relevant to vertebrate development.

Klaus Kalthoff's Biology 349 site at the University of Texas-Austin: Klaus's site contains a convenient index of movie listings (many from this web site!)

Bill Wasserman's Developmental Biology site at Loyola University, Chicago: Contains links to images and movies, including materials from this site, covering a wide range of topics.

Leon Browder's Virtual Embryo site at the University of Calgary: an early, classic online resource in developmental biology

Judith Cebra-Thomas's lab course site at Swarthmore College: nice staging series for common developmental biology model systems used in lab courses

Scott Gilbert's Zygote site: older site with interesting sidelights in developmental biology, originally designed to supplement earlier editions of Scott's text.

Anna Ross's Biology 211 (Vertebrate Embryology Lab) site, Christian Brothers University: many links to useful materials for embryology lab courses.

Online Galleries
Gallery pages at the Center for Cell Dynamics, University of Washington: George von Dassow's incredible resource covering mostly invertebrate species. A huge number of time lapse movies and 3d reconstructions of immunostained embryos, beautifully presented.

The microscope station at the Exploratorium: Outstanding Flash-based time-lapse sequences of sea urchin, mouse ES cell, chick heart, and zebrafish development.

Rachel Fink's site at Mt. Holyoke College: Several clips from videos she has produced for Sinauer, and clips generated by her and her students, including echinoderms and teleosts.

Society for Developmental Biology's Developmental Biology Cinema: movies of fly morphogenesis, calcium dynamics in Medaka, filopodia in sea urchins, and neural crest microsurgery.

Organism specific sites
C. elegans
Bob Goldstein's movie page: Movies (including some from my lab) of many developmental events in C. elegans.

Ed Munro's research page at the Center for Cell Dynamics, University of Washington: movies of very early development in C. elegans.

Wormatlas: Images of worm anatomy, digitized classic papers, and nice diagrams.

WormBook: Chapters on many aspects of C. elegans development, downloadable as free PDFs, including embedded movies in several chapters.

Developmental biology section of WormClassroom: Educational site on C. elegans early development from Fong Mei Lu, Kevin Elicieri, and John White, University of Wisconsin-Madison.

Drosophila
The Anatomy pages at FlyBase: Images and morphed movies of Drosophila development, at the one-stop Drosophila online database.

The Interactive Fly: Database of Drosophila development and conserved molecular pathways in higher eukaryotes, with links to formation of specific anatomical structures.

FlyMove: Incredible Flash-based tutorials and animations covering many aspects of Drosophila development.

Dorsal closure movies from Paul Martin's laboratory, Univ. of Bristol, Alfonso Martinez Arias' laboratory, Cambridge Univ., Mark Peifer's laboratory, Univ. of North Carolina, Dan Kiehart's laboratory, Duke Univ., and Antonio Jacinto, Instituto Gulbenkian de Cięncia, Portugal.

Bill Sullivan's laboratory, U.C. Santa Cruz: movies of cellularization, pole cells, and the blastoderm.

Echinoderms
The Sea Urchin embryology site (SUE) at Stanford University: Many animated GIFs and teaching resources for sea urchins, especially for K-12 education.

Mark Terasaki's video essay, Mol. Biol. of the Cell (1998): great movies of cortical granule exocytosis, fertilization, calcium dynamics

Jan Ellenberg's laboratory at EMBL, Heidelberg: Movies of oogenesis, adult in aquaria, and early development.

Michael Aitchison and Michael Whitaker, Univ. of Newcastle-upon-Tyne: movies of calcium dynamics in sea urchin embryos.

Shuster laboratory, New Mexico State Univ.: Movies of sea urchin cleavage.

Xenopus and other Amphibians
Atlas at XenBase: The descriptive section of the Xenopus database, including a movie page with links to several useful movies (some are incorporated into this site).

Huw Williams and Jim Smith at Cambridge University: great overview movies of Xenopus laevis early development.

Enrique Amaya's laboratory, Cambridge University: Movies of Xenopus tropicalis gastrulation and neurulation.

Dave Shook's gallery in Ray Keller's laboratory at the University Virginia: Wonderful, high-resolution movies of gastrulation in Xenopus and Ambystoma.

John Wallingford's laboratory at the University of Texas-Austin: images and several nice movies from John's research, including movies of Xenopus and Ambystoma neurulation.

Supplementary materials for Ray Keller's 2002 Science article on convergent extension: Movies of amphibian and zebrafish gastrulation (some the same as at the Gastrulation and Shook sites mentioned above).

Dominique Alfandari laboratory, U. Mass.-Amherst: Movies of cranial crest migration.

Zebrafish
Mark Cooper's FishScope site, University of Washington: confocal movies of various developmental processes in zebrafish embryos.

Paul Myers' movie galleries at the University Minnesota-Morris - both old and new: movies of zebrafish development, calcium dynamics, and more.

The flipbook movie from Don Kane and Rolf Karlstrom: low magnification overview of zebrafish development.

Supplementary materials from Development papers from Carl-Phillip Heisenberg's laboratory, Max Planck Institute, Dresden: Montero et al (2005), and Ulrich et al (2003).

Supplementary materials from Nathalia Glickman and Charles Kimmel's 2003 Development paper: movies of notochord and somite development

Chuck Kimmel's lab's movies at the University of Oregon: hindbrain and cranial crest movies.

Erez Raz's laboratory, Max Planck Institute, Göttingen: movies of primordial germ cell migration. See more movies from Weidinger et al (2001) and Doitsidou (2001).

Chicks
Gary Schoenwolf's laboratory, University of Utah: movies of neurulation and primitive streak formation.

Movies by Paul Kulesa and Scott Fraser, California Institute of Technology (note: Paul is now at the Stowers Institute): neural crest in the hindbrain.

More of Paul's movies hosted at Mark Hill's Embryology site.

ChickScope, Beckman Institute, California Institute of Technology: K-12 site devoted to chick development.

Claudio Stern's laboratory, Oxford Univ.: Tutorial on chick development

Cornelius Weijer's laboratory, Univ. of Dundee: Dev. Cell (2004) paper on FGFs and the primitive streak.

Mammals
The Multidimensional Human Embryo site at the University of Michigan: Viewing and virtual slices through Carnegie stages of human embryos.

The Edinburgh Mouse Atlas Project: 3d reconstruction and slices through various stages of mouse embryos, including 3d images of various germ layers.

Embryo Images Online at the University of North Carolina: Interactive tutorial, including many SEM images of developing mammalian embryos.

Transgenic Core Facility, Max Planck Institute, Dresden: movies of pronuclear injection and blastocyst injection in mice

Janet Heasman/Chris Wylie laboratory, Cincinnati Children's Hospital Medical Center: germ cell migration in mice

Human Reproductive Technologies
Dr. Najeeb Layyous' clinic: movies of various reproductive technological interventions in human patients.

Reproductive Medicine Associates: movies of various reproductive technological interventions in human patients.