I bought a Mac Mini to use as a media center. Great, except I found an important feature lacking: you need a keyboard to shut it down (unless you buy Remote Buddy, which for me, was no solution for several reasons). I adapted the frontpython code a bit and created an icon. Et voila: a Shut Down plug-in for Front Row.
You can download it freely from dinkytunes.com; if you like it, please leave a message at the website.
[robg adds: I've seen a number of posts on various sites about how to shut down from Front Row without a keyboard attached. I've mirrored the current version of the file [6.2MB download] here on macosxhints for easier downloading. If you're reading this hint sometime after its posting date, however, you may want to use the linked site, as there may be updates there that won't be reflected here. I haven't tested this one.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20090126113549325