Would be wonderful to have an outer ring showing the sub-menu items, centred on the original parent..
http://fpscomponents.com/images/products/scr_2_silverlight-piemenu.png

The above hasn't aligned the sub-menu items with the parents (very strange!).
Here's an illustration showing good alignment...
http://www.codeproject.com/KB/menus/522343/Menu1.png

Fingers crossed!