Other
Michigan State University: Isomers
This in depth article on isomers has sections that range from basic information to stereoisomers. A section with diagrams is also included.
Auburn University
Auburn University: Isomerism and Stereochemistry [Pdf]
A PDF format file from the Auburn University that explains stereoisomers.
Other
Bristol University: Structural or Constitutional Isomers
Structural Isomers are molecules which have the same molecular formula but have different connectivities (The Order They Are Put Together). Alkanes can be very simple examples of this. This pages shows a few examples.