Wordpress category navigation drop down menu

Anyone know how to make a list of categories and have child categories drop down on hover of the parent category? Im trying to figure out how the code would look like to put in the header.

An example would be like net.tutsplus.com how they have tutorials and videos articles and all.

I know how to do it manually but want to figure out how to do it in php so it would be dynamic.

Thanks for any help.

Well the dropdown/hover bit is done on the browser-side - so relies on JS/CC.

I found a bunch of examples through a simple Google search: http://www.google.com.au/search?q=wordpress+navigation+menu+dropdown