High Priority is exactly what I've been looking for. No more. No less. It even incorporates flexibility I didn't know I wanted, but I appreciate now. It's unobtrusive, elegantly designed, and I love that I don't need iCal running to check (or check off) items on my to-do lists.
The new features added in 1.1 include the keyboard shortcut to invoke the menu that I was hoping for, so I'm completely happy with this lean little utility now. And at only $6 for a personal license, High Priority is worth this meager amount just to support developers like this. If you use iCal, try HP -- you'll be using it and loving it within 30 seconds of downloading.