usb8x is a free, open source application for the TI-84 Plus calculators. It combines a low level driver to support the calculator's USB port with a limited selection of device drivers. It is designed with two goals in mind: First, to allow programmers to create external applications/programs that use USB devices without any knowledge of the low-level workings of those devices or the USB port itself. Second, to allow programmers to create additional drivers for other USB hardware not currently supported natively in usb8x.
The current release version of usb8x is 0.12.