US Department of Energy
Fus Ed Web: Physics of a Fundamental Energy Source
An excellent resource on nuclear fusion! Using incredible graphics and excellent discussion, this site (with its several pages) provides an exhaustive online course on the topic. Click on the link for "a Guided Tour" and begin.
Other
Lcid: Comparison of Fission and Fusion Processes
From the Science Teacher's Resource Center. A data sheet tabulating the many differences between nuclear fission and nuclear fusion. Technical information about the nuclear reactions, the mass defect, isotope masses, etc. is included.