City University of New York
Brooklyn College: The World of Cells: Prokaryotic Cells
A very nice introduction to this group organized in a concise, easy to follow format.
ibiblio
Ibiblio: The Virtual Cell: Cell Biology
In this interactive site, you are presented with a picture of a cell and a description of the structure and function of the parts of the cell. Pictures are colorful and the explanations are short but informative.