A number of sites have reported on the appearance of Aperture on Amazon, according to some customers of Amazon they have received an email stating that Amazon has already received copies of Aperture but is unable to ship it too the public.
Image not in archive — Aperture
"Apple Aperture Post Production Tool for Photographers (Mac DVD) on hand, we are not able to ship it to you until its official release date, November 30, 2005.Many manufacturers, publishers, and record labels restrict retailers from selling or shipping their products until the official release date."
[Update 1] Apple has posted a shipping time of around 1 week on the US store.
[Update 2] Apple has updated the Aperture page confirming that Aperture is now shipping to some customers, it is unknown whether Aperture will be available in Stores in Monday.