Mark Jaquith did a session at WordCamp London on caching. He probably knows as much as anyone in the world on the topic. Fortunately, Duncan Stuart took some really helpful notes on his session.
Included in the notes is a link to Cache Buddy, a plugin Mark just released that “makes more WordPress pages cacheable.” Particularly, it helps you cache pages that need to show logged in data, which is awesome.
I really look forward to seeing this one on WordPress.tv, but until then Duncan's notes are fantastic.