Memory maker Kingston has figured out a way to shoehorn 256GB of memory into a diminutive USB thumb drive.
The DataTraveler 300 offers transfer rates of up to 20 MB/sec. read and 10 MB/sec. write, and supports Windows ReadyBoost (Vista).
Unfortunately, the device is (for now) only available in Europe and the UK for a lot more than a haypenny: £565.67, or approx. $924.