I joined the Visa Business Network a few days ago because they were offering a $100 Facebook ad credit for signing up for a free service.
I set up my first Facebook ad campaigns earlier this week. The one that has been most successful was one that I targetted to people who had links to giraffe-related groups.
That ad linked directly to my pop-up giraffe card listing.
Within hours of the ad going live, I'd sold a giraffe card! It was to a man who had never purchased from etsy before...
Mind you, I haven't sold anything since then, but it's fun to experiment, especially as it's free advertising (at the moment).
I have a friend who linked her ads to her Facebook fan site and she's gotten a TON of new fans as a result! I may try the same thing (while it won't lead directly to sales, it's a lot of fun plus you have people that you can contact for sales, etc).
Here are some links about this offer:
Let me know how things go for you!