Conventional dry cleaning isn't even slightly green. The standard solvent is perchloroethylene (or perc). It is a central nervous system depressant, and is listed as a hazardous air pollutant under the federal standards. There are three less toxic alternatives: GreenEarth, a silicone-based solvent used in modified dry-cleaning machines, liquid carbon dioxide used in high-pressure cleaning machines, and "wet cleaning" with regular water in computer-controlled washing machines. A couple of years ago Consumer Reports did a test of all three of these alternatives. They found that the carbon dioxide gave the best results, even better than conventional dry cleaning (a list of cleaners using carbon dioxide can be found here). A close second was the silicone-based GreenEarth cleaner (a list of such cleaners can be found here). Wet cleaning didn't fare well in their tests.
[by Justin Thomas]