libopencm3
A free/libre/open-source firmware library for various ARM Cortex-M3 microcontrollers.
Generic USB
Here is a list of all modules:
[detail level 12]
 Generic USBLibraries for Generic USB
 Generic USB DriversGeneric USB Drivers
 Generic USB Control RequestsGeneric USB Control Requests
 Generic USB Standard Request InterfaceGeneric USB Standard Request Interface
 Generic USB DefinesDefined Constants and Types for Generic USB
 USB Audio Type DefinitionsDefined Constants and Types for the USB Audio Type Definitions
 USB CDC Type DefinitionsDefined Constants and Types for the USB CDC Type Definitions
 USB DFU Type DefinitionsDefined Constants and Types for the USB DFU Type Definitions
 USB HID Type DefinitionsDefined Constants and Types for the USB HID Type Definitions
 USB MSC Type DefinitionsDefined Constants and Types for the USB MSC Type Definitions
 USB DriversDefined Constants and Types for the USB Drivers
 USB Standard Structure DefinitionsDefined Constants and Types for the USB Standard Structure Definitions
 USB Private StructuresDefined Constants and Types for the USB Private Structures
 USBlibopencm3 LM4F Universal Serial Bus controller
 Usb_msc