Javascript: Get a Value from a Drop Down Menu

To get the value:

document.getElementById( 'dropdownmenu_id' ).options[ document.getElementById('dropdownmenu_id').selectedIndex ].value

To get the Option Name:

document.getElementById('dropdownmenu_id').options[ document.getElementById('dropdownmenu_id').selectedIndex ].text

if you use prototype.js framework then you can replace the references to 'document.getElementById' with a $