I have found myself using less of VirtualBox these days, since I can now sync my iPhone 3Gs and Windows Mobile from Ubuntu, Outlook 2007 works amazingly well with Crossover Office. But I have VirtualBox just in case I want to run iTunes or Paint Shop Pro etc.
Latest screenshot on Ubuntu 9.10 (attached wallpaper):
I changed the XP taskbar to the same color as the panel color to a more integrated look
Edit: The Ubuntu menu is actually the mintmenu (I simply change the menu icon and change the wording to say "UBUNTU")