Various people have commented on solvents for lacquer and shellac
(if you're not into organic chemistry, skip to the next article).

For shellac, most people seem to recommend pure methanol, usually
obtained from industrial suppliers, although some also suggest
denatured ethanol (methylated spirits).

Bill Chapman comments on using MEK as lacquer thinner, although what's
usually sold in paint stores as lacquer thinner is a toluene and acetone
mix.  Better brands seem to have less acetone.  One brand of lacquer
thinner lists its contents as 55% xylene, 30% acetone, 20% alcohol,
and 10% ethyl acetate (plus others).  Another is 50% toluene and 17%
methanol (plus others).  MEK seems like it would be more expensive.

It actually appears that lacquer may be dissolved in any one of the
simple benzenes (benzene, toluene, xylene) or ketones (including
acetone).  Shellac may be dissolved in alcohol or acetone.

Any way you look at this, most of these are really nasty solvents --
they burn, they're easily absorbed through the skin, they can burn you,
and they can cause all kinds of interesting genetic mutations.  Check
the material safety data sheet (MSDS) for anything you buy or use.

You can always find interesting things at Wikipedia:

  http://en.wikipedia.org/wiki/Category:Solvents
  http://en.wikipedia.org/wiki/Lacquer 
  http://en.wikipedia.org/wiki/Shellac 
  http://en.wikipedia.org/wiki/Acetone 
  http://en.wikipedia.org/wiki/Toluene 
  http://en.wikipedia.org/wiki/Alcohol 

A list of MSDS for popular art products:

  http://intranet.risd.edu/departments/envirohealth/msds.asp?oID=ID 
  and http://intranet.risd.edu/departments/envirohealth/msds.asp 

z!
Carl Zwanzig