Animated SN2
This site has a nice animated illustration of an SN2 reaction.
Detailed Bimolecular Substitution
An excellent overview of second-order substitution reactions, including solvent effects, nucleophilicity, and stability of the leaving group.
SN1 Reactions
This site includes a movie and discussion of an SN1 reaction.
First-Order Substitution
Another tutorial on first-order nucleophilic substitution, and issues with carbocation rearrangements.
E2 Reactions
This site has an excellent discussion of E2 reaction mechanisms, great animation, several molecule types, and mechanistic discussion.
E2 Summary
A brief summary of important factors in E2 reactions.
E1 Reactions
A thorough introduction to E1 reactions.
Competition
An overview of substitution and elimination reactions, including competition between elimination and substitution, and first- and second-order reaction mechanisms.
Periodic Table
This link provides access to a very nice electronic periodic table.
Virtual Modeling
This site has a virtual modeling set (Chime or Rasmol required).
Organic Practice
This site has multiple-choice questions on organic chemistry.