Mac OS X only: You might be familiar with the QuickCal system from its Dashboard widget or iOS app. If not, you should get familiar with it, because it's now a full-fledged Mac app that makes adding iCal events speed-of-thought fast.
Adam P's main gripe with QuickCal's very handy widget version was, simply, that it was a widget. Not everybody likes widgets, and having a menu-bar-docked app, he wrote, would have made it perfect. Now, basically, that app exists. Hit a keyboard shortcut (Command-Shift-C by default) and up pops a small window. Type in a calendar appointment the way you'd describe it to your imaginary secretary — "Meeting with Tim on Friday at 3pm" — and QuickCal fills in all the fields, based on how you structured your event. You'll learn a few of QuickCal's nuances over time, but you basically don't have to learn anything, other than working the shortcut into your muscle memory.
Along with the basic input power, QuickCal can also provide "smart reminders" so that events you add that are a few hours away ping you, say, 30 minutes ahead of time, but events you're adding for three months from now hit you up a week before the event. It makes you realise just how goofy the "default reminder" scheme on most calendar apps really is.
QuickCal Desktop is a free download for Mac systems only.
QuickCal Desktop 1.0 – Released! [Smelly. Puppy.]