Own UpTo

Almost cooler than those giant desk calendars everyone had in the '80s, UpTo lets you share events from your iCal/GCal/etc with specific groups you create (Friends/Work/Family/People Named Shane), displays a handy color-coded heat map that shows how busy you are on any given day, and even lets you comment on other people's events (say something hilarious about that weird Shanes-only party!).