I use the notes section to describe what the website I'm bookmarking is all about. If the website tells you straight on its page what it does, you can now add it almost automatically to del.icio.us.
Simply select the block of text, then proceed to bookmark the page. I used Firefox, which gives me a pop up window. As you can see in the pop up, the notes section is filled up with the relevant highlighted block. See the picture above.
I cannot imagine I only just found out about this.