I don't know if this is a no-brainer, but I thought I'd submit it...
Now that Mail messages and iCal events and To-Dos are individual files, it's possible to create aliases to these individual items using Spotlight. If you do a search in the Spotlight window (not the menu item -- the Command-Option-Space curfull-sized window), you can Option-drag or Command-Option-drag any result to a folder or the desktop to copy it or create an alias.
I used this method to create an alias to a specific email that I wanted to reference from the desktop. Now, when I double-click the alias, Mail starts up and opens that specific email for me automatically!
Mac OS X Hints
http://hints.macworld.com/article.php?story=20050511184458622