You can find your listings by one of the following methods:
Click your username in the top right of the site and then click "Your Content" in the drop down menu.
Click "Home" in the top navigation, then you can either click "Watched Forums" or "Watched threads" from the sub-menu.
For the Marketplace, once you reach the maximum allowed active posts, a popup will occur showing the active threads so you can easily close one to open a new one.