accessible ajax update panel

This useful article about an Accessible ajax update panel doesn't just provide a simple trick to make ajax controls more accessible but will also help developers understand how screen readers interact with Web pages and reiterates my point about using headings.

fly out menus

If you want to use fly out / drop down menus in your Web application, consider the suckerfish family of open source menus:
Suckerfish Dropdowns

and

Son of Suckerfish Dropdowns | HTML Dog

and
Suckerfish Dropdowns - Perciformes!

A simple google search for suckerfish accessible menus will yield these and other useful links for implementing such menus.