Depending on the type and subject matter of the art you’re trying to sell, consider searching around for websites and discussion groups that encourage selling of your type of art. For example, I sculpt and mold porcelain animal figurines, one of which was an Afghan hound. There’s a Yahoo! group called caninecollectibles that allows (even encourages) posting of sale items from private artists, and I sold out within fifteen minutes of posting. There’s a similar, and much more active, group, devoted to “breakable” (ceramic and factory resin) animal figurines, primarily but not exclusively horses. I took a chance and posted when I had some extra tadpoles to sell. Not only did I sell those out within a day, I had to make some emergency trips to the kiln to create more to meet demand. Never expected a crowd composed primarily of horse collectors who buy a few other animal figures to be so enthusiastic, but it worked.
To cultivate a following, many of the artists within the circle I’m involved in start their own Yahoo groups (some stray from Yahoo, but most of their market already has Yahoo accounts so they tend to cluster there) to encourage discussion, input, and that sense of community that goes a long way toward increasing sales. I maintain an opt-in mailing list of previous customers and people who wander in through my website, and rarely do I not sell out long before I need to market through other venues.
Probably goes without saying, but carefully select the groups you post to for appropriateness, and examine the list’s rules scrupulously before posting. You don’t want to be pegged as a spammer. If you have a website showing your work, it’s often a smart idea to write an intro message that includes a link to your site rather than posting a direct sales pitch. Sure, I got away with selling tadpoles to horse people, but I was within the group’s stated guidelines and was a well-known list member before I posted there.
Might be worth googling up the line of “Poor Richard’s” website books. I remember there being one about marketing your work via the web that included some smart suggestions for individuals and small businesses.