After experiencing a vibrating sensation from the front of my '98 Sable
when braking, I just replaced the rotors and pads this morning.  The
brake'n'shake (and we helped!) problem is now fixed.

However!!!

Before changing the discs and pads, I had been noticing that the front
seemed to vibrate even when not applying the brakes.  I assumed that the
rotors were just so badly warped that the pads were being sideswiped every
time the wheels turned.  But now, after replacing the rotors, the vibration
is still there—not when braking—just when coasting, maintaining speed, or
accelerating.  When I'm traveling in a straight line, the vibration is
hardly noticeable.  When I have to go around a curve in the highway, the
vibration becomes very pronounced and I can hear a mild "fwapfwapfwapfwap"
sound from the front.

So I jacked up the driver's side.  I can't wiggle the wheel from top to
bottom, but I can wiggle it from front to back.  At the front edge of the
tire, there's about 1/4" of slack in it.  The wheel, spring, strut, and the
heavy bolt at the top of the strut inside the engine compartment all move
when I wiggle the wheel.  Plus, there's a short bar attaching the strut to
what appears to be the stabilizer bar.  That short bar wiggles, too in
relation to the wiggle of the wheel.

I tried the same thing on the passenger side.  It's tight and there are no
problems there.

What are your assumptions based on this?  Ball joint?  Tie rod ends?
Defective cigarette lighter?

Thanks,
Damaeus