We have recently improved DJ-Menu and DJ-MultiTreeMenu joomla module mootools menus by the responsive option for small screens.
Starting with JM-Wedding06 responsive joomla template we're using our joomla menus that are richer in the new responsive option.
Both menus include "Display SELECT for small screens" parameter that transform the horizontal menu into select dropdown box for mobiles, tablets or netbooks and other handheld devices, shortly devices with small screens that are narrower than 960px;
Take a look at the parameter of the menu:
And this is how the menu adapts to fill the screen area of devices:
Download and check it for free.