Below is a collection of entertaining videos:

• Sphere Eversion: How to turn a sphere inside-out.
• Not Knot: This video explores life in the knot complement. (Also good for understanding quotient spaces!)
• Hexaflexagons: A series of videos about a craft with nice symmetries.
• Look Around You (Maths): Answers to all the questions about MATHS you never knew you had.
• Tadashi's Toys: A series of videos about "strange" physical phenomoena that Tadashi Tokieda has demonstrated with toys.
• Chladni Plates: When tones are played on these plates, the corresponding nodal set takes on some gorgeous "patterns."

Some ways that math has been used to inspire or create art:

• M.C. Escher: Escher is perhaps best known for his drawing of "impossible" situations and tessellations of the hyperbolic plane.
• Sketches of Topology: The author of this blog takes constructs in low-dimensional topology and creates graphical representations of them.
• Fractals

... And I would be remiss if I didn't include links about Klein bottles:

• The Adventures of the Klein Bottle: A short nicely answering the essential question "what is a Klein bottle?"
• Acme Klein Bottle: Developed by Cliff Stoll, you can buy your very own Klein bottle paraphernalia!
• Torus Games: A series of games played on the torus (or Klein bottle!) developed by Jeff Weeks.

I hope to add more to this page soon.