SoundSource is the only spotted app that comes to mind.
PlugSuit is Leopard only but only because it is unnecessary in Tiger. Most of the big Leopard-only uber-upgrades that were promised have yet to be delivered and even then, they are Leopard only versions, not apps. So SoundSource is the only thing that I run that falls in to your category.
Oh, if you like to do lists there is
Anxiety which uses the new iCal integration, but I don't like computer to do lists because I often don't want my item removed when I mark it complete, so I use the desk pad in front of my computer or stickies on my computer.