I have Redbubble and have made about $0.50 when I sold a card.

I have better luck with Flickr, PR, and my personal website. I've had one contact through PR/Flickr and one through a Google search for a specific subject that led to my personal website and a few through Flickr, but none of the Flickr ones have actually gone through.

Most of my business has come from face-to-face contact.