Here's a useful little data-mining script to extract the del.icio.us tags most often used against recently posted items. Put the script on your web server, change the value of the $ID variable to your del.icio.us identity and you'll get a list of tags the del.icio.us community has used to describe the stories you've posted. Note that it uses PHP's built-in JSON parser which isn't available till 5.2. You may have to strip slashes from the page body before parsing the JSON data on line 100 depending on your magic quotes setting.
It would be simple to get the script to extract the identity from a query on the request URL, but I'm afraid of how useful providing such a service could be to people. Probably the right way to do this is to distribute the HTTP GETting and data manipulation to the browser with JavaScript instead of doing this on the server side. This works fine, though.