I'm not sure if this is documented anywhere, but I found something interesting in the CDs & DVDs preferences panel. Click any pop-up menu with Option key pressed and a hidden menu item titled "Options..." appears at the bottom of each pop-up. It opens small dialog box with a "Perform action at login" checkbox.
Probably as expected, but if you check this, your assigned action will perform at every login time. You can see the settings in the ~/Library -> Preferences -> com.apple.digihub.plist file.
[robg adds: I'm not sure why you might want to do this at login, but it is interesting...]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030421030316566