I was recently working on a custom Drupal 6.x module that needs to create a custom content type with fields upon installation. I did quite a bit of hunting for how best to do this. There are a few different approaches, including using the Features module, or having my module do all the node and db handling, etc. I decided to use the export and import features of CCK, and it's very easy to do. Here is a link to the handbook page at DO that explains how to do it.
If you're a Drupal developer, you're aware, no doubt, of the coming of D7. One of the exciting changes in D7 is that CCK has been brought into core...somewhat. The changes provide opportunities to do things that were much more difficult to do before, but also, might create a black hole of challenges in the migration space between D6 and D7.
I had the need to add an image tag to page output that was generated inside a custom Drupal module. I had retrieved the image's FID (file ID) from the CCK field, and needed to get from there to having an ImageCache version of the image displayed. I'd done it within a view by selecting the appropriate field format in the Views UI, but how to do it in code? Like many other tasks in Drupal, the solution turned out to be easier than the hunt for it.