In case you are still interested, Amazon.com and Wal-mart finally have some Xbox 360 bundles in stock.

They still do not sell unbundled Xbox 360 consoles.
The bundles are selling out quickly, but restocking again. Every time I check another bundle is gone or back in stock. So at least there is some movement in the Xbox 360 supply situation.

Currently those bundles are in stock on Wal-mart:
Xbox 360 Customer Choice Bundle with Hard Drive sells for $838.52
Xbox 360 Premium Bundle With Spherex Surround Sound System sells for $998.82.

Amazon.com has spotty availability of this Xbox 360 Premium Bundle:
Xbox 360 Pro Gamer's Bundle with 6 games - Mature

I only listed Xbox 360 Premium bundles, I do not think a Core system is worth it. BensBargains Xbox 360 Tracker works pretty well to find a Xbox 360 in stock.
With the still unknown launch date for the Sony PS3, Microsoft can take their time to get to a normal supply situation. Especially if you own a HDTV it is very tempting to get a Xbox 360.
More Xbox 360 offers.