You can use Flickr or Deviant Art to display your work. I've found Flickr to be very good, though it does not permit you to use it for commercial purposes. It has groups into which you can enter your work, and you can comment on other user's work, which is fun and interesting.
Deviant Art is irritating- jargon ridden and much slower than Flickr to upload stuff onto. Saachi has a free hosting site and so does MyArtSpace. I haven't really explored these.
You could also try Ebay.
My feeling is that the web is primarily a reference for those who'll already seen your work in reality: one is fairly unlikely to sell much to people who've only seen your work online because art is expensive and because photos do not give a perfect impression of what a piece really looks like, and the risk of making a dubious purchase is simply too great.
I also write a blog, to help people understand what I’m working on: http://tadeuszderegowski.blogspot.com/
Offline I recommend- local art groups, competitions, holding shows with similar artists, studio parties, making postcards and handing them out, art fairs, and charity auctions. Send images to magazines too. Show work in restaurants and bars. Collaborate on projects with other artists or writers. Try to find a local community of artists so you get the benefit of group shows and moral support.
Most of the efforts you make will not bring immediate results, so don't be surprised if a year after you've started pushing your work about you still haven't sold anything. The market for art is VERY small... but Persistance Pays.