http://www.box.co.uk/they have a really good one, as the main element clearly demostrates a more arrow, then loads down to a magazine style menu that has it's main header a different style to the subheadings
All very easy to view in a hurry.
Whilst on this subject, i utilise a not so fancy similar stlye menu on my shop part of my site but when in phone/mobile display you would need to lock down to maybe a set number of menu items.
e.g.; rather than displaying all menu options in mobile phone mode, you could choose to just display top level, 2nd. level etc. before they have to click to choose, otherwise mobile devices would just see a tonne of menu options and not much content and are likely to switch straight off the site