Clunk-clunk-clunk

[Michael McLaughlin]

Today my '95 90 Sport Quattro developed (or, more likely, I finally 
noticed) an odd noise. It comes from the left rear wheel area, and 
happens only when accelerating -- it's a 
clunk-clunk-clunk/knock-knock-knock type of sound, and it varies with 
speed. And, like I said, it happens only when accelerating, whether 
it's at parking-lot speeds or on the highway.

Any ideas what it might be?

Thanks,
Mike McLaughlin