At first I was just using Geek Tool to output my Crash Reporter log and Console.log to the desktop so I could see if / when Quicksilver crashed silently and what my computer was doing, respectively. I added System.log to the mix, and left it at that until I found a rather old article on Mac OS X Hints that explained how to use Geek Tool in more depth.
In the Mac OS X Hints article, they mention an iTunes output that displays the currently playing iTunes track. Even though I have Quicksilver monitor tracks on change, I still need to press a button to see the track info. This method seemed like an easy, low memory-usage method of always knowing what I was listening to. Unfortunately, the information in that article left the script a bit buggy, i.e. iTunes would open right back up again as soon as the script is called, there is no output when iTunes is paused, etc. I edited the script using bits and pieces of my own knowledge and an excellent Now Playing script for Adium. I put this script in ~/Library/Scripts/Applications/iTunes and called it every ten seconds from Geek Tool using
<code>osascript /path/to/scripts/iTunesName.scpt | iconv -f utf-8 -t ucs-2-internal</code>
et voilà, the song I am listening to is on my desktop AND I can close iTunes without it opening back up again. You can get the script I used here(http://fiveuptons.com/thomas/iTunesName.scpt.zip).
In addition to the logs and iTunes, I display the output of
<code>ps xm -O %mem</code>
truncated to just the first five processes, and the
cal output mentioned in this Mac OS X Hints article. I also display the contents of my Desktop and Download directories on my Powerbook’s display when I am at home on my 20” Cinema Display so that I can see what is contained in those folders when I am doing something fullscreen like watching a movie.