I dont know what it is called but you can see on this page http://carleypelletier.deviantart.com/gallery/#_browse if you click on a category you'll get a list and if there is a subcategory there will be a > at the end. When clicking this the menu text moves left off the menu and the new categories are in. How do i do this type of menu? i'm open to any libs. It would be nice if i can fill it using json or a config file.
Check this Chinese menu of jQuery drop downs, you are looking for a "drill down style of menu, on the menu you will see a "jQuery iPod-style Drilldown Menu" which is pretty close to what you want, they just used multiple ones.
A working example of one is here