Bring back the floating desktop clock
With the release of OS X 10.5, we gained hundreds of new features. We also lost some, including the option to have a floating desktop clock (via the Date & Time System Preferences panel). Now the only time display option is in the menu bar. If you'd like to get it back -- and you have a copy of OS X 10.4 -- it's actually quite easy to do.
On your 10.4 machine, navigate to this directory (you'll have to control-click Menu Extras and choose Show Package Contents from the pop-up menu if you're not pasting this into the Finder's Go » Go to Folder dialog):
/System/Library/CoreServices/Menu Extras/Clock.menu/Contents/Resources/
In that folder, you'll find WindowClock.app. Copy it to your 10.5 machine, and drop it in your Applications folder. Launch it, and you'll find it works -- and you can even control-click on it to switch between digital and analog mode (your changes here will also affect your menu bar clock). You might think you're done, but there's a bit more work yet to do. First, the ownership on WindowClock.app wasn't quite right on my machine, so I changed it to match the other apps in Applications with this Terminal command, within the Applications directory (you could also leave it as owned by your user without any downsides, I believe):
sudo chown root:admin WindowClock.app
Next, the biggest problem with WindowClock is that it's a faceless background application -- so once you've launched it, you need to use Activity Monitor or Terminal to quit it. There are two ways around this problem: you can turn it into a regular application, or you can control it via an AppleScript. Read on for both solutions, as well as a way to tweak the floating clock's transparency.