I use are
http://fineartamerica.com/ and
http://www.redbubble.com/people/spidersknee I call them double-duty sites because they function as online art galleries but also foment communication between artists and viewers. They both are part of the burgeoning print-on-demand trend, which as an added benefit is more economical and sustainable that traditional printing. FineartAmerica tends to have more North American members, but Redbubble originates from Australia and claims a global roster of thousands of artists and writers.
Of the two, I've found Redbubble to be the more vibrant and inclusive online community, but both have numerous print options, if you are interested in making prints of your work available to potential buyers.
Oh, and both are free, although I think FineartAmerica has subscription options for those who want their own websites.
Check 'em out!