Unobtrusive connected select boxes (Chris Heilmann)
The interface element of connected select boxes (one select box changing the options in the other one) is one of the most used and also most annoying elements of web application design. While it works nicely for anyone having JavaScript enabled and using a mouse it can be a nightmare to use with a keyboard (unless you know that you can expand the whole list with alt+cursor down first). (Article dated: March 17, 2007)
