Now using wp-cache
DreamHost sent me automated notices that I was using over 100 CPU minutes a day on slaw.dreamhost.com, a web server with over 300 accounts. In other words, I was using at least 1/60 the capacity of the quad-core server. I guessed that a lot of my CPU usage was from the 10,000 hits a day for The Burning Edge's feed, so I installed wp-cache for The Burning Edge. The plugin doesn't seem to break anything; I think it invalidates its entire cache when anything changes (except for templates).
Installing the plugin for The Burning Edge reduced my CPU usage to about 55 minutes a day, low enough to stop the automated notices but still not within the desired range of 30-40 minutes a day. I just installed it for this blog too.