How to display node/add/sometype form on another page?

Question

The whole problem is following:

Lets say we have Items, Items can have Bids, Items can have Questions and Question can have Answer.

When an Item is displayed

Answer 1

The Module Form Block is the easiest way to embed a node form on a page. Then I would use views with a block display and an argument to show a tabular listing of these related nodes.

Although the Drupal 7 comment module is built on fields it really isn't quite flexible enough for non comment like things. If you want your sub-type to have a title and body then comments is probably the way to go. If you only want custom fields then a node is the way to go and possibly using something like Automatic Nodetitles.

Update for 2014: If adding a block without coding is preferred by anyone you may wish to check out Advanced Form Block module, which adds a few features to your standard blocks (you can add as many as you like, make them all submit via AJAX and even select which fields you want). Unlike the Form Block module it is still actively maintained for Drupal 7.