Illuminated Sounds has released Random7, a free random MIDI generating program created with MAX/MSP.
It is basically a 8 step sequencer that outputs midi by randomly selecting from the 7 notes in the various scales pictured above, and also randomly selects the velocity of each of the notes. The layout is very simple, the drop down menu lets you select your scale, noteout lets you choose your midi i/o, the start/stop button does just that, the knob adjusts speed, and you can click on any of the red spots to trigger a note manually.
Random7 is available for Windows and Mac.
Check Illuminated Sounds for more information and some demo sounds.