I know of two systems that take your RSS feed in your shop and then feed it into Twitter or Facebook.
There is TwitterFeed and Dlvr.it. I have used both and I prefer Dlvr.it. It has been more reliable but both work in very similar ways.
In order for both to work you need to sign up to an account with them. I'm going to show you how to setup dlvr.it but Twitterfeed is similar and you should be able to set that one up in a similar way.
First you need to locate your shop RSS feeds.
On Etsy, it's here
and on Folksy it's here
This will give you a webpage covered in text and numbers that apparently makes no sense. The important part you need is the URL or web address at the top of the screen. Once you have that, you can add the feed to dlvr.it.
Click 'add route'and it will be added to the main screen.
You have two things to do next, set up the source (so where your feed is coming from) and set up the destination (where the information is going to). Click the add button next to 'Sources' and select 'New' for the feed. Paste your feed into the Feed URL box. Then click 'save source'.
To add a destination, click the add button next to 'Destinations' and you can select the various accounts you want to feed into. To set up Twitter, select 'new' next to the twitter icon. This will then prompt you to log in and authorise your twitter account. Then click 'Save'. This will do the basics of sending your URL and title to Twitter. To add your Facebook (or other accounts) click 'Add' next to 'Destinations' again and add the next account. You can add to Tumblr or multiple twitter accounts or any number of social networking sites.
There are some options that you can do to add text to each tweet but the amount you can add is limited.
To edit a Source or Destination, click on the pencil icon next to each item. As you can see from the above image, I send my shop feed to Facebook and Twitter. I also have specified that I want it to go to my Facebook fan page rather than my personal page.
So, when you list or relist on Etsy or Folksy, it will automatically tweet your listing. You need to set up a route for each shop and I have even got it set up for my blog. So when this publishes, you may just have read it, because of this tool.
Thanks for reading and if you have some questions about Dlvr.it, ask me in the comments!