Here is a great site that has links to various parts of episodes of Seinfeld which relate to economic concepts.
The Economics of Seinfeld. It is the simplicity of Seinfeld that makes it so appropriate for use in economics courses. Using these clips (as well as clips from other television shows or movies) makes economic concepts come alive, making them more real for students.
Below is a funny clip about the black market for shower heads. Worth a look.