Some mechanics that my brother took his '92 Passat to last week to find a
battery drain had a pretty simple way to track it down.
Put a multimeter on the battery that shows the drain.
Start pulling fuses in the fuse panel until the drain stops.  Look up in the
manual what the fuse controls and you will have it pretty narrowed down.

For him it was his automatic seat belt system that seemed to work fine, but
there was a switch that the mechanism was supposed to hit when it moved to
the end of it's travel.  Apparently this switch was worn out and even though
you couldn't hear it or anything the electric motor that moves the seat belt
mechanism was running all the time.
They moved the seat belt mechanism to where it would normally be when someone
is in the seat and then disabled the electric part.  Now they just have to
undo two belts when getting in or out of the car, but at least their battery
doesn't keep going dead.
Thanks,
Ken Wilford
http://www.vanagain.com
John 3:16
Phone: (856)-765-1583
Shop:   (856)-327-0027
Fax:     (856)-327-2242