Wikipedia article
MathWorld article with rotatable images 
Imaging maths - Inside the Klein bottle
by Konrad Polthier
Distortable image of Klein bottle and other surfaces
Message
in a Klein Bottle 
The
Klein Bottle in Four-Space
Animations by Tom Banchoff, who has been making computer movies to illustrate geometric ideas since 1970.
The Klein
Bottle by Tom Banchoff with Jeff Beall: movies and interactive
versions- Acme Klein Bottle. This is a
company that sells glass Klein bottles.
