title: Magento: Addon Products
body: <p>I'm looking to create "Addon Products" in Magento.  What I mean is:  If the product were a Greeting Card, and you were to add that to your cart, you might be presented with options on the checkout page to add an "Envelope"  or "Stamps".  These would be separate products with their own prices, however, they would not be available otherwise in the store. In other words, some sort of "Linked / Child Products" that only become available once the "Parent" product has been added.</p>
  
  <p>Does this sort of product configuration exist within Magento?  Doesn't seem to be a Bundled Product.</p>