Here are three versions of collapsing menus. The first has sections which open and close independantly so all content can be seen at once. The second opens menus individually and, if a menu is open when another is accessed, that menu will close as the new menu is opened. The third and final menu is much like the second only the menu opening waits until the current menu has finished closing before it begins to open. Speed is variable.

Menu items for these menus are added manually. This makes the menus less dynamic, but also allows full control over the items and their customization (plus its easier for those less accustomed to scripting). Simply create menu clips with a title movieclip named title, place them in the menu movieclip and the menu's script pretty much takes over from there assigning the titlebar actions (for opening and closing menus) automatically. All you would need to do is name and add button actions for each item in the menu, whether they are getURL's or frame navigation (or anything else you want).

Note: Since masking is used in these menus, its a good idea to use pixel-snapped pixel fonts for your text if you intend to keep it crisp.