I just saw somebody using a del.icio.us widget to post a new URL to his account. I’m using a bookmarklet instead which looks like this:
Note that this is actually one line!
Instead of »YourUserName« fill in your del.icio.us username and create a new bookmark in your favourite browsers. Name it »del.icio.us« or whatever you feel is right. As URL you fill in the bookmarklet. Whenever you want to post a website just go on the website and click on the del.icio.us bookmark you created. It will bring you to del.icio.us with some form fields already filled with text like URL and Title and other neat things. After saving your post you will return to the website you just saved.