Why not just re-direct to something like coral cache, like this wordpress plugin does:
http://elliottback.com/wp/archives/2...for-wordpress/
If a referral comes from a high traffic site like digg, it sends it to the cached version instead. You could do it on site, or re-direct to a pre-existing cache off site. Maybe even only activate the re-direct once a certain number of hits per minute are registered, or something of that nature.