Nokia AMOLED N85 is $556 unlocked
Nokia's $556 N85 lands at Amazon with a "list price" of $1,200 — "You save $644.01!" — but the site cautions that it will arrive after December 24th.
The N85 is a GSM/WiFi model that runs Symbian and has a 5 megapixel camera and GPS. The stout price, however, is explained by its active-matrix OLED display. According to Nokia, this gives it a higher resolution at a bigger size than passive OLED technology: 2.6" at 320x240.
Nokia N85 Unlocked Cell Phone--U.S. Version with Warranty (Copper) [Amazon via OLED-info and Engadget]

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Will this one be as crippled as the US N95 for lack of firmware updates?
Why does a quad-band gsm phone need a separate US version anyway?
You can almost certainly get it cheaper by buying a SIM free (unlocked) UK version http://www.mobilefun.co.uk/product/17425.htm
at £381 including the 15% VAT (sales tax)
It's been available for pre-order on Amazon for a while. I had one sitting my cart waiting to see an actual date, which a few days ago started showing the dreaded "after Dec 24th" message.
I picked up an N82 instead, losing US 3G - which my current plan doesn't have anyway - and that fancy OLED screen, but gains a proper flash for the camera. (The year-old N82 has a Xenon flash while the N85 uses LED).
@1&2, the US needs separate versions because its 3G networks use different frequencies from everybody else. A UK version will only do 3G in Europe and Asia.