Folks who turn on their Xbox 360 today will find a system update waiting for them. This is the previously mentioned update which allows you to use USB Memory devices with your console as a replacement for memory cards or, for the desperate, a hard drive.
Just as a reminder of how it's all going to work, you'll have to have a USB storage device with at least 1 Gb of space on it. The maximum amount of storage you can use -- regardless of the device's maximum -- is 16 Gb and each console can have up to two devices registered to it.
Kinda makes the 512mb memory card I bought so long ago feel really out of date, but I'm looking forward to being able to keep all my Rock Band DLC on my keys so that I can more easily play it wherever I am. Plus, I'm sure it will be helpful for some who've either never bought a larger storage option or refused to due to their exorbitant prices.
Xbox 360 System Update – USB Memory Support [Major Nelson]