Optics Java Applets (1)
 

The wavelength (and speed) change, not frequency when light enters different media.  (other applet)
Derivation of Snell's law from geometrical considerations (with wavefronts).
Snell's law from a point source in many media
The world from the point of view of a fish.
Total internal reflection for a curved lens.
 
Excellent older java applets for optics

Non-working(?) links
Law of reflection java applet
(Try level 2 on this) You might like to use the law of refelection to approximately play pool.
Refraction - reflection with wavelets from Huygen's principle (nice).

One of my favorites: a light under a swimming pool. (non working)