I've been taking a break from RM to get familiar with some things I haven't had time to get familiar with, such as SpamAssassin and GPG. I found Paul Graham's discussion of antispam techniques interesting, although it took me a while to get through some of the supplemental material on Bayesian filtering.

There was a time when I knew probability pretty well, but I don't remember much of it, not having used it (more than trivially) in over ten years. Also, having to go over all this stuff again keeps me from spending more time on other things I like to do, such as practicing piano.