Drop Down Menus

Horizontal Drop Down Menus from A List Apart
http://www.alistapart.com/articles/horizdropdowns
Article on creating horizontal drop down menus.

Dynamic Drive
http://www.dynamicdrive.com
Lots of scripts for menus and navigation using CSS and DHTML, from Dynamic Drive, a specialist DHTML site.

Infinite Menus from OpenCube Advanced Navigation Solutions
http://www.opencube.com/imenus.asp
Their drop down menus look good and can be created using a visual designer.

Sothink
http://www.sothink.com/
Have a number of tools for creating DHTML menus. Some can be used as a Dreamweaver extension.

Drop Down Menus at del.icio.us
http://del.icio.us/search/?all=drop+down+menu
Links to drop down menus at social networking site del.icio.us.

Xtreeme DHTML Menu Studio
http://www.xtreeme.com/dhtml/
Has plugins for popular web design software.

Likno AllWebMenus - Javascript / DHTML Menu Maker
http://www.likno.com/

Open Cube Infinite Menus