Amazon Treo600/AT&T page. Seems to have just been posted, as it lists the standard not stocked or discontinued notation:
http://www.amazon.com/exec/obidos/tg/detail/-/B00013AU0G/qid=1070812296/sr=-2/ref=sr__2_etk-cell/103-4312958-3186229?v=glance&s=wireless&n=301185

Guess the unlocked Cingular won't be available thru Amazon, if at all, til after Tmo gets it shot...