Regardless if you have the most sophisticated caching mechanisms in place (like WP Super Cache), the simplest and most effective way of surviving flash traffic from sites like Digg is to redirect the traffic to a mirror, like the free CoralCDN.
I personally think that the Coral Content Distribution Network is one of the most amazing yet underrated web invention in recent years. It’s so effective yet simple to use it’s like magic to end-users. By loading a URL like “http://www.tummblr.com.nyud.net/archivepage/“, that page is fetched and cached on the CoralCDN, which is a peer-to-peer network comprising of servers all over the globe. So Digg can send thousands of users to my CoralCDN mirror and use no more of my host’s resources and bandwidth than if a lone visitor hit my site. Read more about Coral on their homepage.
Without further ado, here is the .htaccess code that will redirect visitors from high traffic sites like Digg to your CoralCDN mirror.
# Heavy Site Redirect to Coral Cache # Links incoming from heavy sites are redirected to the Coral Cache # Exception: Coral Cache Proxy Servers # Exception: Googlebot crawler # # CONFIG: Replace “yourdomain.com” with your target domain name. # CONFIG: Follow the HTTP_REFERER RewriteCond examples to add or remove # domains to the list of redirected sites. # <ifmodule mod_rewrite.c> RewriteEngine On RewriteCond %{HTTP_USER_AGENT} !^Googlebot RewriteCond %{HTTP_USER_AGENT} !^CoralWebPrx RewriteCond %{QUERY_STRING} !(^|&)coral-no-serve$ RewriteCond %{HTTP_REFERER} ^http://([^/]+\.)?digg\.com [OR] RewriteCond %{HTTP_REFERER} ^http://([^/]+\.)?slashdot\.org [OR] RewriteCond %{HTTP_REFERER} ^http://([^/]+\.)?slashdot\.com [OR] RewriteCond %{HTTP_REFERER} ^http://([^/]+\.)?fark\.com [OR] RewriteCond %{HTTP_REFERER} ^http://([^/]+\.)?somethingawful\.com [OR] RewriteCond %{HTTP_REFERER} ^http://([^/]+\.)?kuro5hin\.org [OR] RewriteCond %{HTTP_REFERER} ^http://([^/]+\.)?engadget\.com [OR] RewriteCond %{HTTP_REFERER} ^http://([^/]+\.)?boingboing\.net [OR] RewriteCond %{HTTP_REFERER} ^http://([^/]+\.)?del\.icio\.us RewriteRule ^(.*)?$ http://www.yourdomain.com.nyud.net/$1 [R,L] </ifmodule>
Credit: Benjamin Yu
Note: Removed “:8080” from “http://yourdomain.com.nyud.net:8080/” since CoralCDN now runs on port 80, the standard HTTP port. Yay! 
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