I noticed that a lot of us try to sell components from our Instructables to other users, but there's not really a standardized way of doing so.
In my spare time, I created a site that allows us to do just that! You can see the featured post in the forum here
, but I thought a nice how-to article might help, as well!
The marketplace is a third party site, but I think it is great because you can put the link to the items you're selling in your Instructables, browse other user's items, etc :)