Etsy
Etsy the best known of these sites, primarily because it has been operating the longest. To become a seller you simply sign up and create your own shop. They also provide you with buttons and banners for you to promote your shop. Each item costs $0.20 to list and if after four months it hasn't sold it will be unlisted. Whenever you make a sale you will you be charged a sales fee of 3.5% of the selling price. Etsy is US based, but has buyers and sellers all over the world.Visit Etsy
Artfire
For sellers Artfire offers two levels of membership. With the basic level you can sell your stuff for free - no listing or final sales fee whatsoever! For this you have your own shop (or studio as they prefer to call it) with promotion tools, including the ability to sell directly from your blog. The premium account costs you $12 per month and naturally includes a number of additional features including preferred placement in searches and the ability to use the community functions of the site.Visit ArtFire
Da Wanda
Da Wanda is aimed at the European market - specifically the UK, Germany and France. It follows a similar format to Etsy in that you have your own shop, although I am not sure if they provide you with any promotional tools. Currently there are only listing fees on the German version of the site, although there are plans to introduce these on the UK and French versions soon. Selling fees are 5% of the final selling price.
Visit Da Wanda
Folksy
Folksy is a UK based site, again following a similar principle to Etsy, so you have your own shop and they provide badges you can put on your blog. Currently it is only open to sellers in the UK, (although you can buy from anywhere in the world that accepts Paypal), but it is planned to expand to other parts of the world in the near future. Fees are £0.20 listing fee and 5% selling fee. Items are listed for 6 months.Visit Folksy