See ExpressCard.

The third generation PC Card from PCMCIA that superseded the CardBus. Introduced in 2003 and designed for both desktop and mobile use, ExpressCards use USB 2.0, single lane PCI Express or both interfaces at the same time. At 75 mm long, ExpressCards are slightly smaller than 86 mm PC Cards. Available in 34 mm and 54 mm widths, the 54 mm slots can accommodate both sizes.

An Internal USB Solution
One advantage of the ExpressCard is that it eliminates the need to carry an external USB storage device and cable. For example, a USB hard drive or flash drive can remain within the laptop when traveling, with, at most, a small protrusion jutting out from the side. See PC Card.