Halp Calander software

Google Calendar, Outlook's calendar, Thunderbird + Lightning addon (really guys, just implement the two together already), Sunbird, Windows Live Mail, Yahoo/Hotmail, etc...
 
blackberry calander is nice, but there's something holding it back from being 'very nice' that i can't quite put my finger on..

other than that, i use post it notes for irl reminders.