I really like caching - to the point that I have buggerized the carefully tuned cache-coherency used by squid.
Its interesting to see that this, complete with my incredibly optimistic squid.conf file will speed up most accesses significantly from a vanilla squid cache setup.
One thing that I have been meaning to do, but havent gotten around to it yet is to fix past-expiry pages. The evil people at imdb serve you their little icons with an expiry date months in the past. I want to capture that in the original caching request and invalidate the expires: tag.