Here is a top 10 select list of articles I compiled on advanced theming techniques (or similar topics):

Drupal 6:

• Revise the structure, layout, and visibility of your node fields
• Overriding the themable output for anything part of your theme using the Devel module
• Creating a custom theme layout for a CCK node form
• Generate HTML for an individual CCK field
• Embedding a View in Drupal 6 using views_embed_view

Drupal 5:

• Creating dynamic theme layouts based on the contents of your regions
• Creating a Block View that shows Related Content using Taxonomy and Arguments
• Embedding a view in a page or node layout
• Custom theming based on a node's taxonomy
• Creating an alternate theme layout for certain pages