Reader Alex writes in with his ubergeeky solution for quickly posting new events to your Google Calendar using an AutoHotkey script and a small command line utility.
To setup the same shortcut key for yourself, you'll need to extract the script and utilities to a directory, add your Google Calendar account information to the logon.txt file, and then after launching the script you can use Win+G to show the dialog for adding an event to Google Calendar. He's included a compiled version in the package, but the source code is included if you want to change the hotkey to something else.
Hit the link for the download and full write-up, including the source code for the utility. If you'd rather integrate your quick-add capability into Launchy, you can use the command-line executable to do so, or you can use the Google Calendar plugin.
AutoHotkey: Quick Add to Google Calendar [Just an Asterisk]