Since Blosxom 3.0 do not have static rendering so far, I wrote a plugin called BlosxomCache for speeding up Blosxom.
It works as /cache/. User's request will be cached so that the same page won't be needed to regenerate every time. Users will not see the dirty page use this plugin. The more plugin you use, the more CPU you save in your box!
Note that the database entries are not going to be deleted, so you might want to delete the database on the first day of each month (But it's harmless if you don't do it unless your disk is full).