Any way to create a horizontal Drop Line type menu?

Im looking for a way to style my menu as a horizontal Drop Line menu where you mouse over and the sub links are displayed inline underneath the main links.

Here is an example: http://www.cssplay.co.uk/menus/drop_line.html

Currently I have the Nice Menus module installed and if there is a way to simply style it horizontally like that it would be easiest. If not any other solution would be great.