Lh-usb is a set of bindings for the Linux usbfs interface for writing usb device drivers from user-space. It uses some SBCL-specific functions, particularly the SB-ALIEN FFI.
I wrote the original hack which became lh-usb while trying to figure out how to talk to an mp3 player which was unsupported in Linux. While I did manage to figure out the communications protocol, I have yet to build a nice user (or programmer) interface for the mp3 player. As it was once supporting code for an exploratory hack, lh-usb still has some rough edges, to say the least.