There’s a widget in the Presentation panel of WordPress hosted blogs, which allows you to add an RSS feed to your side-panel, but it doesn’t always work.
The trick is to paste your RSS feed into feedburner.com.
Go to your profile page on digg.com and copy the URL to the clipboard..
Now go to feedburner.com and paste the clipboard into the panel shown below..
Click ‘Next’ and, if you’re not already a Feedburner user, quickly sign up for a free account. Once you’ve done that (and feel free to explore other feedburner tools for future reference), in the ‘My Feeds’ page, you should see another RSS icon next to your newly created feed, like so…
Copy the feed into the clipboard once again and paste it into a new RSS widget in wordpress’ Presentation panel. You might have to add another RSS widget using the “How many RSS widgets would you like?” box, below the “Available Widgets” panel…
Feedburner correctly formats the RSS feed from your digg.com account, so that every time you ‘digg up’ a story, it appears correctly in your wordpress.com hosted RSS widget.