Sadly, the mini's temperature sensors aren't exposed to Mac OS X (before you go suggesting solutions, it's a G4 mini, and using the search box on this site will show that I've already found utilities for other machines), and the same goes for SMART status of disk drives and a bunch of other minor things.
Still, I can't complain about lack of information:
And yes, one of these days I'll get around to posting my feather-weight micro-stats framework (basically a couple of shell scripts plus a Python script that parses an XML spec for the graphs), since the number of official users has since doubled - Melo made a few tweaks to it to monitor his MacBook Pro.
In the meantime, and as a sort of sinchronicity wrap-up for my home migration, I recommend that people wanting to put together their own setup to get rid of all that image-based Spam (for themselves or for their users) take a look at Bruno's OCR approach.
Although my fresh SpamAssassin install has now reached critical mass and is able to clear out the vast majority of Spam, both gocr and netpbm are readily available in MacPorts, so I am likely to give this one a go if Razor can't cope.