LidRock was a token of appreciation from movie theatres as they ditributed CD's in lids when they served large sodas=LidRock. I'm not sure what happened to LidRock but I do know that through this a few artists have become mainstream and successful.
The CDs were discontinued in 2003 but rumor has it that LidRock may be making its return to theatres and on top of sodas sometime in the fall of 2011.