Microsoft is officially announcing the Zune HD Release date is September 15th, but the 16/32GB Zune HD can be pre-ordered today.

The Microsoft Zune-HD features:

Microsoft AMOLED touch screen. Allows you to easily flip through music, movies and other content. The 3.3-inch glass screen and 16:9 widescreen format display (480x272 resolution) offer a premium viewing experience.

Amazon has launched a pre-orde Web page for the Microsoft Zune HD with a 3.3 inch AMOLED Display. At this website we will see the 16GB model for 220$ and the 32 GB version for 290$. At the moment pre order is not ready because it returns an website not found error.
via Amazon.com

After the first mp4 player from Cowon S9 with an AMOLED, Sonys NWZ-X-Serie now Microsoft bring out a new multimedia player with an OLED Display.

Engadget.com about the Zune HD OLED Display;

For a few weeks we reported about some rumors and now its official the new Microsoft Zune HD mp4 player comes with an 3.3 inch 16:9 type capacitive OLED screen with multitouch. The resoultion is 480x272 pixel.

From the Press release:

There are some more rumors that the new Microsoft ZuneHD comes with a capacitive, multi-touch Am-oled Display with an 16:9 aspect ratio.

The rumors also says that the ZuneHD device will come in 16 and 32 GB versions, and will support wireless sync. It will also finally come with a browser that supports multi-touch.
The new ZuneHD will support also 3D Xbox games, but in that case there is not clear how!
The launch is planned around 3-4 quarter in 2009.