There are several that I know of:

ARTCRIT
PAINT-L (mostly for painters)
ARTLIST
EAS-URI (Univ. of Rhode Island's Experimental Art Society--a quiet one)
ART-ENVIRONS (mostly about art in the environment and outsider art)
WAL (Women's Artist List)

I used to get ArtCrit but it got too in-crowd-y for me.  Paint-L is good for
technical tips and the odd philosophical discussion.  ArtList has a lot of
flamers for a listserv but is OK.  EAS-URI is quiet and is run by a
musician, but they discuss art as well.  Art-Environs is fun but frequently
wanders off-topic.  WAL is also good but very militantly feminist, which
some people may not like.

I also check rec.arts.fine occasionally and there can be some good talk on
there, if you can get past the flame wars.

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Have fun!

Julia Moore
Indianapolis Art Center