Gamestop / EBgames announced during a quarterly conference call that they will be accepting preorders starting October 10th at all of their brick and mortor stores.  All preorders will require a $100 down payment which can be made in cash/credit or trade-in. 

Reserves are reported as extremely low with less than 10 units per store for the intial launch batch.  Top performing stores may have up to 15 units.  This is for the initial batch, so of course more will follow.

Here is the complete blurb from the Gamestop email newsletter:

Limited PlayStation 3 Pre-order
GameStop and EB Games will begin accepting limited pre-orders for the PlayStation 3 console on Tuesday, October 10, on a first come, first served basis. Due to extremely limited supply, we expect to deplete this allocation very quickly, most likely in minutes. We will not accept additional pre-orders at this time. To avoid an unnecessary trip we strongly recommend you call your local store to determine availability. A $100 reservation deposit is required, which can be funded with cash, credit or trade. As we cannot control production and shipping issues by the manufacturer, a reservation deposit does not guarantee receipt of a system available to purchase at launch. Reservations/Purchases are limited to 1 per household.

Our limited online pre-order program will be announced at a later date, after software and accessory availability dates are confirmed. Online product pricing and availability will vary and will be fulfilled independent of store reservations.

Good luck and let us know how you make out!