Another brilliant piece of Mac OS X software that was recently ushered out the gate: Fantastical. It specializes in fast, elegant calendar management via a natural language engine and event creation hotkey (assignable by you). It’s similar in concept to something like 37signals’ Backpack calendar (Update: 37signals in the last few years has shifted focus to just their Basecamp product; as such, here are a list of alternatives to the defunct Backpack software), but far more sophisticated in its understanding of semantic syntax.
Rarely can you mention Mac OS X software without noting the developer’s carefully crafted website for it. Fantastical’s product page is great (another reason I hope these pages outrank Apple’s proxy pages for the iTunes/App Store listings in organic search), with an enjoyable subtle use of modern HTML5/CSS3 animations for product feature emphasis and clarity.