Fresh from the clogged tubes of teh intarwubs…
"I have read many “tutorials” which told users to modify WordPress core files. This is a really, really, bad idea. Why? Simply because you’ll have to modify that file again when you’ll upgrade your blog. Here’s how to overwrite WordPress core function without modifying any core file."
"I really like the well known CSS technique called “Sliding doors”. Unfortunely, WordPress functions as such as wp_list_pages() and wp_list_categories() don’t allow yo to embed span elements in your code. Here’s how to bypass it, with some php regular expressions."
An accessible guide to what CMSs are good for; I shall show this to prospective clients, methinks.