Possibly the Novation X-Station 61. I use the 49-note version and it's the handiest keyboard I currently own. The X-Station is a VA synth with built-in effects, and a MIDI/USB controller and audio interface. I like the fact that the knobs have real-world functions/names instead of generic designations like "S1". And the keybed feel is outstanding. A laptop and an X-Station is a complete portable studio.