We roll with the open source zen cart shopping cart software here (details on what we use here) – but we’re always looking around at other shopping cart systems, not just for ourselves, for other makers that are trying to sell their goods online. Here’s one called “Goodsie” – looks like Tumblr-ish + shopping cart. If you have shopping cart services and systems you’re interested in post up in the kit biz forums or in the comments!