Der Onlinedienst zur Zellbiologie mit Videos und interaktiven Medien
cells.de

Milestones in Cell Division: A specially written series of short articles on the main discoveries that have shaped the field of cell division
nature.com/celldivision/

Eukaryotic cell division; The Cell Cycle
ultranet.com/~jkimball/BiologyPages/C/CellCycle.html

Synapse Web, "structure of hippocampus, dendrites, axons, astrocytes, synapses, and associated organelles. For experts, Josef Spacek's Atlas of Ultrastructual Neurocytology, with over 400 high-quality images detailing the ultrastructure of the central nervous system, is a valuable resource..."
synapses.bu.edu

Histology World
zyx.freeservers.com/histo/histo.htm

Wagner-Hossler Microscopic Anatomy Images
udel.edu/Biology/Wags/histopage/histopage.htm

Color Images of Histological Sections. "GIFs of light microscope images archived according to tissue type and organ systems."
udel.edu/Biology/Wags/histopage/colorpage/colorpage.htm

"Transmission and scanning electron micrographs are archived according to tissue type and organ system. These are meant to compliment the light microscopic images and reveal structural detail not observable by light microscopy."
udel.edu/Biology/Wags/histopage/empage/empage.htm

"Three dimensional models of tissue and cell structures have been constructed and rendered to provide realistic interpretations of volume structures not evident in two dimensional tissue sections."
udel.edu/Biology/Wags/histopage/modelspage/modelspage.htm

Miscellaneous cell and biology images:
itg.uiuc.edu/exhibits/gallery/
Cellular structures:
itg.uiuc.edu/technology/atlas/structures/

Heuser Image gallery
heuserlab.wustl.edu/images.html