DVForge has started shipping its GuitarPlug and MicPlug miniature USB audio adapters, which plug directly into an electric guitar, bass, or dynamic microphone converting the analog signal to a high quality USB audio signal.
Both adapters measure just 2.3"x1.8"x.7". The GuitarPlug is compatible with single or double coil pickups, with active pickups, while the MicPlug features an XLR connector. They are compatible with any Mac OS X audio software that accepts a 16-bit, 48KHz USB audio signal.
The GuitarPlug and MicPlug require Mac OS X 10.2.8 or later and cost $49.99 each.