Product page at M-Audio: http://www.m-audio.com/products/en_ca/MobilePreUSB.html
2 x 2 16-bit/48kHz analog I/O
2 microphone inputs (XLR balanced) with 48v phantom power
stereo microphone input (1/8”)
2 high-impedance instrument/line inputs (balanced/unbalanced 1/4” TRS)
2 mono line outputs (1/4” @ -10dBV)
stereo line output (1/8”)
stereo headphone output with level control knob
gain control knob for each input channel (+40 dB max)
zero-latency hardware direct monitoring (mono/stereo) with software level control
USB-powered
As of April 2011, it can be purchased on Amazon for ~ $100 USD
There are no additional drivers required.
All features work in Linux.
Personal experience (forum user nealfunkbass): I have owned a MobilePre for several years, and it has worked out-of-the box on every Linux distribution I have tried (Ubuntu, Fedora, Arch, etc).