Get an Xbox 360 Arcade + 20GB hard drive for $134.99
It's a refurb, but it's also the lowest price I can recall on an Xbox 360. And the bundled hard drive is one massive gob of icing on the cake.
The Xbox 360 Arcade comes without a hard drive. That's bad.
The Xbox 360 Arcade bundle at MacMall comes with a 20GB hard drive. That's good! Especially considering the price: $134.99, plus about $12 for shipping.
The only catch: It's a refurb, meaning you get a 90-day warranty. I have no idea if Arcade models have the same red-ring-of-death gene as other Xboxes; someone more knowledgeable on the subject will undoubtedly speak up in the comments (hint, hint).
In any case, I'd be surprised if this didn't sell out quickly, so I'm just going to leave it there. If you're looking for an Xbox on the super cheap, you've found it.
(If it does sell out, check back later for another deal. You know I won't leave my cheap-peeps hanging!)
Backup deal (sort of): Happy Free Shipping Day! Over 700 merchants are offering free shipping today, and promising delivery no later than Dec. 24. (Alas, MacMall isn't among them.)