In Drupal, is there a way to create new content (based on a content type that uses CCK) in a popup or lightbox or similar technique?
There are at least two worlds that I know of:
http://drupal.org/project/popups_reference which uses http://drupal.org/project/popups
and
http://drupal.org/project/noderelationships which uses http://drupal.org/project/modalframe
Both of these are about creating the node in a modal in order to reference it via a node reference field. There might be ones for more general purposes, or you could probably adapt one of those. I've been enjoying noderelationships lately. Haven't tried the other recently.
The projects sprugman refers to are useful when you need to create a referenced node while you're adding another node. If you simply want to make the /node/add/[contenttype] link to open in a lightbox, try the Lightbox2 module.
There is a great module in Drupal automodal that works with Modal Frame API. What you need to do is simply add a new class 'automodal' to your links... and the magic is done for you.