M-Audio Controller KeyStation 61ES

Top Features
61-note velocity-sensitive semi-weighted action
pitch and modulation wheels; volume/control slider
separate MIDI out jack routes MIDI signals from your computer to control external devices
powered via USB or 9VDC power adapter (sold separately)
Mac OS X, Windows XP, and Vista (32 bit) class-compliant for plug-and-play
includes Ableton Live Lite music production software, so you can make music right away