It's nothing special. The <li>'s are floated, basically. That's it. Then this style is applied to each anchor (they have each anchor defined separately) :).
background: url(../GFX/Global/Nav.png) -545px top;
The "sexiness" of the menu is just the image there. The text-indent takes away the text you'd put inside the anchor of the HTML and hides it so that it won't affect the view of it. It'll come back though if CSS is off :).
Here is the link to the image in question.
The bottom part of the image I linked is used as the hover state. That image I linked to is a CSS sprite. It combines multiple images into one file for less HTTP requests.