Three weeks ago I mentioned Gregg Pollack and Jason Seifer's great page caching tutorial. In that short time, and mostly on the back of that article, they've gotten 1000 subscribers and thousands of page views. Their tutorials are good!
Not ones to rest on their laurels, they've now written and released the second part of their caching tutorial series, focusing on action and fragment caching. They don't go into insane levels of detail, but cover action and fragment caching reasonably comprehensively and provide lots of illustrative code snippets. And for those developers using Edge Rails, they also take a quick look at ActiveRecord query caching.