Ezolde is a kind of serial (SPI or UART protocols are supported, see separate downloads below) to USB converter. However it's different from most such devices. Instead of a virtual COM port, it emulates a keyboard and sends the data as keystrokes. This way it gets around the limitations of CDC mode projects (such as e.g. AVR-CDC), but has obvious other limitations.
For a complete list of projects based on V-USB see Objective Development's projects list.