I know wordpress gets slated on digg everytime the site goes over but it helps if you have wp-cache installed. A newer cache wp supercache is also available that gives fully static pages.
In general don’t have too many unneeded plugins particularly those that use sql.
It may also help to have a simplified theme you can switch to if digg is causing problems. For example Wordpress themes are split in to different files, index.php, header.php, footer.php sidebar.php. These can be consolidated in to one file which should help. Less images would also help.
Another tip I saw was to disable comments during high traffic from digg. From what I can see anyway everyone from digg justs posts comments on digg and ignores the sites comment form anyway.
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