Can you provide some more details? What kind of caching do you use? Some in the cms or on the server? Do you know if your hosting provider is using squid?
I am using stock Wordpress 2.7.1 (2.7.0 at the time of slashdot effect). I have not enabled any caching plugins at Wordpress. All the pages are generated with php, so I suspect it is impossible to effectively use squid? Here's the website itself: http://www.cybertechnews.org