Good questions. I have a Facebook fan page, and try to post to it a couple of times each day. I also use that page to "fan" other crafters, and we chitchat there. It's a good way to build a network of like-minded folks. And we give shout-outs for each others items, so the non-crafting fans see those as well.
http://www.facebook.com/pages/Self-Rescuing-Princess-Society/172306996146449I'm also on twitter as myself, and I use that to send out links a couple of times a day to my items or my shop.
http://twitter.com/#!/itchbayI have a blog, where I talk about a variety of issues, and sometimes include info about what I'm working on or selling.
http://karenish.wordpress.com/But I'm toying with the idea of setting up a blog specifically for my items, and separating that out of my personal blog.
I haven't really explored any of the other services like Tumbler, or Stumble Upon, but they're on my list to investigate.
I feel like I need to get my items out to a wider audience than just my friends and their friends.