Let this site do the work for you!
This is more of an informational bit than an actual article like I usually write...
If you're one of the many who is still trying to get your hands on an XBox360 and have lost all hope of your preorder ever coming in, or just don't want to brave the 100+ person lines outside BestBuy at 3am in the freezing cold, there's still a chance! Through my favorite Gaming resource sites, I found my way to the XBox360 Tracker (http://www.xbox360tracker.com) which automatically checks about 70 online retailers with fair frequency to see if their "stock" status has changed. As soon as a retailer has some available, the site updates with a link, a price and a nice green "IN STOCK" notice next to the item.
There's also an RSS feed you can use to keep up to date without checking the website every 5min.
I highly recommend the site. I just placed an order for a Premium console bundled from CircuitCity and should have it in my grubby little hands by tomorrow afternoon.
So, go check it out and try your luck!
Note: I am in no way affiliated with that site, so I don't get money for referrals or anything like that, I just feel it's a great resource to get ahold of an insanely difficult system to come across.