I think that social websites like Flickr, Facebook and Twitter are very useful for getting people to know you and what you do, so you can have more people visiting your website and spreading your work around.

I don't have much experience at this either, but I like Etsy. It's not a stock images website, which is good. People who visit Etsy want artisan crafts and handmade itens. If you're making your own prints (or they're totaly handmade), it's perfect for Etsy market.