What calendar program do you use?

I am researching an online solution and wondering what folks are using that they like - paper, google, ical, outlook?

http://lifehacker.com/5833572/the-best-calendar-app-for-windows

Google Calendar's biggest advantage is that it's extremely easy to use without skimping on features. Everything is plainly laid out: you can add quick calendar events with a few keystrokes or more advanced events, full of reminders and other attributes when you need them.

Being able to send yourself emails and text messages is also great, as is setting specific events to "free" or "busy". No doubt the coolest feature of GCal, though, is being able to share your calendars with others, and have them share their calendars with you.

Never again will you have to call your spouse and ask them if they're busy, or email your friends asking them what dates they've planned for that road trip. It's all in your calendar, all the time. Plus, it's completely free, and can sync to just about any other app out there, meaning you'll always have it on your phone and can access it from any computer.