I was able to order a new built-to-order Mini 9 with Ubuntu 8.04 last month. I found the link via Yahoo shopping, but going in direct through the Dell sites, it was nowhere to be found. I think they must be making them with the last stock of parts since its technically been discontinued for months? Ubuntu was the only OS option when I ordered. No XP.
Base price was $199. I was able to configure the way I liked and saved the cart, then logged out and logged back in through Bing when Dell was offering an additional 15% cash back. The $15% pretty much covered tax, shipping, and the California Hazardous Materials Recovery Fee.
In the end it was about $20 less than the comparable models were going for in the Outlet at the time.